1.
Geranium
–
Geranium is a genus of 422 species of flowering annual, biennial, and perennial plants that are commonly known as the cranesbills. They are found throughout the regions of the world and the mountains of the tropics. The long, palmately cleft leaves are circular in form. The flowers have five petals and are coloured white, pink, purple or blue, geraniums will grow in any soil as long as it is not waterlogged. Propagation is by cuttings in summer, by seed, or by division in autumn or spring. The genus name is derived from the Greek γέρανος or γερανός ‘crane’, the English name ‘cranesbill’ derives from the appearance of the fruit capsule of some of the species. Species in the Geranium genus have a mechanism for seed dispersal. This consists of a column which springs open when ripe. The fruit capsule consists of five cells, each containing one seed, joined to a column produced from the centre of the old flower. The common name comes from the shape of the unsprung column. However, many species in this genus do not have a long beak-like column, geraniums are eaten by the larvae of some Lepidoptera species including brown-tail and mouse moth. The species Geranium viscosissimum is considered to be protocarnivorous, confusingly, geranium is also the common name of members of the genus Pelargonium, which are also in the Geraniaceae family. These are generally half-hardy plants which are grown from seed every year, or offered as bedding in spring. Linnaeus originally included all the species in one genus, Geranium, other former members of the genus are now classified in genus Erodium, including the plants known as filarees in North America. The term hardy geranium is often applied to geraniums to distinguish them from the pelargoniums, however, not all geranium species are winter-hardy. The shape of the flowers offers one way of distinguishing between the two genera Geranium and Pelargonium, a number of geranium species are cultivated for horticultural use and for pharmaceutical products. Some of the commonly grown species include, All the above species are perennials and generally winter-hardy plants, grown for their attractive flowers. They are long-lived and most have a habit, with palmately lobed foliage
Geranium
–
Geranium
Geranium
–
Showing the "bill" and seed dispersal mechanism of Geranium pratense
Geranium
–
Geranium platypetalum
Geranium
–
Geranium pratense (meadow cranesbill)
2.
Standard atomic weight
–
The standard atomic weight is a physical quantity for a chemical element, expressed as relative atomic mass. It is specified by the IUPAC definition of natural, stable, because of this practical definition, the value is widely used as the atomic weight for real life substances. For example, in pharmaceuticals and scientific research, out of 118 chemical elements,84 are stable and have this Earth-environment based value. Typically, such a value is, for example helium, Ar, the indicates the uncertainty in the last digit shown, or 4.002602 ±0.000002. For twelve elements various terrestial sources diverge on this value, because these sources have a different decay history, for example, thallium in sedimentary rocks has a different isotopic composition than when in igneous rocks and volcanic gases. For these elements, the atomic weight is noted as an interval, Ar. CIAAW also publishes abridged values, and simple conventional values for interval values, the standard atomic weight is a more specific value of a relative atomic mass. It is defined as the atomic mass of a source in the local environment of the Earths crust and atmosphere as determined by the IUPAC Commission on Atomic Weights. In general, values from different sources are subject to variation due to a different radioactive history of sources. By limiting the sources to terrestial origin only, the CIAAW determined values have less variance, the CIAAW-published values are used and sometimes lawfully required in mass calculations. The values have an uncertainty, or are an expectation interval and this uncertainty reflects natural variability in isotopic distribution for an element, rather than uncertainty in measurement. For synthetic elements the isotope formed depends on the means of synthesis, therefore, for synthetic elements the total nucleon count of the most stable isotope is listed in brackets, in place of the standard atomic weight. When the term weight is used in chemistry, usually it is the more specific standard atomic weight that is implied. It is standard atomic weights that are used in periodic tables, the abridged atomic weight, also published by CIAAW, is derived from the standard atomic weight reducing the numbers to five digits. The name does not say rounded, interval borders are rounded downwards for the first border, and upwards for th upward border. This way, the precise original interval is fully covered. For example, hydrogen has Ar, standard = and this notation states that the various sources on Earth have substantially different isotopic constitutions, and uncertainties are incorporated in the two numbers. For these elements, there is not an Earth average constitution, however, for situations where a less precise value is acceptable, CIAAW has published a single-number conventional atomic weight that can be used for example in trade
Standard atomic weight
–
The
atomic number of hydrogen is 1. The standard atomic weight of hydrogen is 1.008 (this value is not given here as an expectation interval, as it is in elements below). Atomic weight is the same as relative atomic mass. The atomic weights of samples of hydrogen will vary according to their content of heavy hydrogen (
deuterium), and this will in turn depend upon where the samples are collected.
Standard atomic weight
3.
Periodic table
–
The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configurations, and recurring chemical properties. This ordering shows periodic trends, such as elements with similar behaviour in the same column and it also shows four rectangular blocks with some approximately similar chemical properties. In general, within one row the elements are metals on the left, the rows of the table are called periods, the columns are called groups. Six groups have names as well as numbers, for example, group 17 elements are the halogens, and group 18, the noble gases. The periodic table can be used to derive relationships between the properties of the elements, and predict the properties of new elements yet to be discovered or synthesized, the periodic table provides a useful framework for analyzing chemical behaviour, and is widely used in chemistry and other sciences. The Russian chemist Dmitri Mendeleev published the first widely recognized periodic table in 1869 and he developed his table to illustrate periodic trends in the properties of the then-known elements. Mendeleev also predicted some properties of elements that would be expected to fill gaps in this table. Most of his predictions were proved correct when the elements in question were subsequently discovered, Mendeleevs periodic table has since been expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behaviour. The first 94 elements exist naturally, although some are only in trace amounts and were synthesized in laboratories before being found in nature. Elements with atomic numbers from 95 to 118 have only been synthesized in laboratories or nuclear reactors, synthesis of elements having higher atomic numbers is being pursued. Numerous synthetic radionuclides of naturally occurring elements have also produced in laboratories. Each chemical element has an atomic number representing the number of protons in its nucleus. Most elements have differing numbers of neutrons among different atoms, with variants being referred to as isotopes. Isotopes are never separated in the table, they are always grouped together under a single element. Elements with no stable isotopes have the masses of their most stable isotopes. In the standard periodic table, the elements are listed in order of increasing atomic number, a new row is started when a new electron shell has its first electron. Columns are determined by the configuration of the atom, elements with the same number of electrons in a particular subshell fall into the same columns. Thus, it is easy to predict the chemical properties of an element if one knows the properties of the elements around it
Periodic table
–
Dmitri Mendeleev
Periodic table
–
Standard form of the periodic table (color legend below)
Periodic table
–
Glenn T. Seaborg who, in 1945, suggested a new periodic table showing the actinides as belonging to a second f-block series
4.
Hydrogen
–
Hydrogen is a chemical element with chemical symbol H and atomic number 1. With a standard weight of circa 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form is the most abundant chemical substance in the Universe, non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed protium, has one proton, the universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays an important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a charge when it is known as a hydride. The hydrogen cation is written as though composed of a bare proton, Hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water. Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing and ammonia production, mostly for the fertilizer market, Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks. Hydrogen gas is flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion is −286 kJ/mol,2 H2 + O2 →2 H2O +572 kJ Hydrogen gas forms explosive mixtures with air in concentrations from 4–74%, the explosive reactions may be triggered by spark, heat, or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C, the detection of a burning hydrogen leak may require a flame detector, such leaks can be very dangerous. Hydrogen flames in other conditions are blue, resembling blue natural gas flames, the destruction of the Hindenburg airship was a notorious example of hydrogen combustion and the cause is still debated. The visible orange flames in that incident were the result of a mixture of hydrogen to oxygen combined with carbon compounds from the airship skin. H2 reacts with every oxidizing element, the ground state energy level of the electron in a hydrogen atom is −13.6 eV, which is equivalent to an ultraviolet photon of roughly 91 nm wavelength. The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, however, the atomic electron and proton are held together by electromagnetic force, while planets and celestial objects are held by gravity. The most complicated treatments allow for the effects of special relativity
Hydrogen
–
Purple glow in its plasma state
Hydrogen
–
The
Space Shuttle Main Engine burnt hydrogen with oxygen, producing a nearly invisible flame at full thrust.
Hydrogen
–
Spectral lines of hydrogen
Hydrogen
–
First tracks observed in
liquid hydrogen bubble chamber at the
Bevatron
5.
Helium
–
Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and its boiling point is the lowest among all the elements. Its abundance is similar to figure in the Sun and in Jupiter. This is due to the high nuclear binding energy of helium-4 with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of nuclear fusion and radioactive decay. Most helium in the universe is helium-4, and is believed to have formed during the Big Bang. Large amounts of new helium are being created by fusion of hydrogen in stars. Helium is named for the Greek god of the Sun, Helios and it was first detected as an unknown yellow spectral line signature in sunlight during a solar eclipse in 1868 by French astronomer Jules Janssen. Janssen is jointly credited with detecting the element along with Norman Lockyer, Janssen observed during the solar eclipse of 1868 while Lockyer observed from Britain. Lockyer was the first to propose that the line was due to a new element, the formal discovery of the element was made in 1895 by two Swedish chemists, Per Teodor Cleve and Nils Abraham Langlet, who found helium emanating from the uranium ore cleveite. In 1903, large reserves of helium were found in gas fields in parts of the United States. Liquid helium is used in cryogenics, particularly in the cooling of superconducting magnets, a well-known but minor use is as a lifting gas in balloons and airships. As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre, on Earth it is relatively rare—5.2 ppm by volume in the atmosphere. Most terrestrial helium present today is created by the radioactive decay of heavy radioactive elements. Previously, terrestrial helium—a non-renewable resource, because once released into the atmosphere it readily escapes into space—was thought to be in short supply. The first evidence of helium was observed on August 18,1868, the line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. This line was assumed to be sodium. He concluded that it was caused by an element in the Sun unknown on Earth, Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος
Helium
–
Helium, 2 He
Helium
–
Spectral lines of helium
Helium
Helium
–
Sir
William Ramsay, the discoverer of terrestrial helium
6.
Lithium
–
Lithium is a chemical element with the symbol Li and atomic number 3. It is a soft, silver-white metal belonging to the metal group of chemical elements. Under standard conditions, it is the lightest metal and the least dense solid element, like all alkali metals, lithium is highly reactive and flammable. For this reason, it is stored in mineral oil. When cut open, it exhibits a metallic luster, but contact with moist air corrodes the surface quickly to a silvery gray. Because of its reactivity, lithium never occurs freely in nature, and instead, appears only in compounds. Lithium occurs in a number of minerals, but due to its solubility as an ion, is present in ocean water and is commonly obtained from brines. On a commercial scale, lithium is isolated electrolytically from a mixture of lithium chloride, the nucleus of the lithium atom verges on instability, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. Because of its relative instability, lithium is less common in the solar system than 25 of the first 32 chemical elements even though the nuclei are very light in atomic weight. For related reasons, lithium has important links to nuclear physics, the transmutation of lithium atoms to helium in 1932 was the first fully man-made nuclear reaction, and lithium-6 deuteride serves as a fusion fuel in staged thermonuclear weapons. These uses consume more than three quarters of lithium production, Lithium is found in variable amounts in foods, primary food sources are grains and vegetables, in some areas, the drinking water also provides significant amounts of the element. Human dietary lithium intakes depend on location and the type of foods consumed, traces of lithium were detected in human organs and fetal tissues already in the late 19th century, leading to early suggestions as to possible specific functions in the organism. However, it took another century until evidence for the essentiality of lithium became available, in studies conducted from the 1970s to the 1990s, rats and goats maintained on low-lithium rations were shown to exhibit higher mortalities as well as reproductive and behavioral abnormalities. Lithium appears to play an important role during the early fetal development as evidenced by the high lithium contents of the embryo during the early gestational period. The available experimental evidence now appears to be sufficient to accept lithium as essential, the lithium ion Li+ administered as any of several lithium salts has proven to be useful as a mood-stabilizing drug in the treatment of bipolar disorder in humans. Like the other metals, lithium has a single valence electron that is easily given up to form a cation. Because of this, lithium is a conductor of heat and electricity as well as a highly reactive element. Lithiums low reactivity is due to the proximity of its electron to its nucleus
Lithium
–
Lithium floating in oil
Lithium
–
Lithium pellets covered in white lithium hydroxide (left) and ingots with a thin layer of black nitride tarnish (right)
Lithium
Lithium
7.
Beryllium
–
Beryllium is a chemical element with symbol Be and atomic number 4. It is a rare element in the universe, usually occurring as a product of the spallation of larger atomic nuclei that have collided with cosmic rays. Within the cores of stars beryllium is depleted as it is fused and it is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl, as a free element it is a steel-gray, strong, lightweight and brittle alkaline earth metal. Beryllium improves many physical properties when added as an element to aluminium, copper, iron. Beryllium does not form oxides until it reaches high temperatures. Tools made of copper alloys are strong and hard and do not create sparks when they strike a steel surface. The high thermal conductivities of beryllium and beryllium oxide have led to their use in thermal management applications, Beryllium is a steel gray and hard metalloid that is brittle at room temperature and has a close-packed hexagonal crystal structure. It has exceptional stiffness and a high melting point. The modulus of elasticity of beryllium is approximately 50% greater than that of steel, the combination of this modulus and a relatively low density results in an unusually fast sound conduction speed in beryllium – about 12.9 km/s at ambient conditions. Other significant properties are high specific heat and thermal conductivity, which make beryllium the metal with the best heat dissipation characteristics per unit weight, in combination with the relatively low coefficient of linear thermal expansion, these characteristics result in a unique stability under conditions of thermal loading. Naturally occurring beryllium, save for slight contamination by cosmogenic radioisotopes, is essentially pure beryllium-9, Beryllium has a large scattering cross section for high-energy neutrons, about 6 barns for energies above approximately 10 keV. The single primordial beryllium isotope 9Be also undergoes a neutron reaction with neutron energies over about 1.9 MeV, to produce 8Be, thus, for high-energy neutrons, beryllium is a neutron multiplier, releasing more neutrons than it absorbs. Beryllium also releases neutrons under bombardment by gamma rays.8 seconds, β− is an electron, tritium is a radioisotope of concern in nuclear reactor waste streams. As a metal, beryllium is transparent to most wavelengths of X-rays and gamma rays, making it useful for the windows of X-ray tubes. Both stable and unstable isotopes of beryllium are created in stars, primordial beryllium contains only one stable isotope, 9Be, and therefore beryllium is a monoisotopic element. Radioactive cosmogenic 10Be is produced in the atmosphere of the Earth by the cosmic ray spallation of oxygen, 10Be accumulates at the soil surface, where its relatively long half-life permits a long residence time before decaying to boron-10. The production of 10Be is inversely proportional to activity, because increased solar wind during periods of high solar activity decreases the flux of galactic cosmic rays that reach the Earth
Beryllium
–
Beryllium, 4 Be
Beryllium
–
Beryllium ore
Beryllium
–
Emerald is a naturally occurring
compound of beryllium.
Beryllium
–
Louis-Nicolas Vauquelin discovered beryllium
8.
Boron
–
Boron is a chemical element with symbol B and atomic number 5. Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is an element in the Solar system. Boron is concentrated on Earth by the water-solubility of its more common naturally occurring compounds and these are mined industrially as evaporites, such as borax and kernite. The largest known deposits are in Turkey, the largest producer of boron minerals. Elemental boron is a metalloid that is found in small amounts in meteoroids, industrially, very pure boron is produced with difficulty because of refractory contamination by carbon or other elements. Several allotropes of boron exist, amorphous boron is a powder, crystalline boron is silvery to black, extremely hard. The primary use of boron is as boron filaments with applications similar to carbon fibers in some high-strength materials. Boron is primarily used in chemical compounds, about half of all consumption globally, boron is used as an additive in glass fibers of boron-containing fiberglass for insulation and structural materials. The next leading use is in polymers and ceramics in high-strength, lightweight structural, borosilicate glass is desired for its greater strength and thermal shock resistance than ordinary soda lime glass. Boron compounds are used as fertilizers in agriculture and in sodium perborate bleaches, a small amount of boron is used as a dopant in semiconductors, and reagent intermediates in the synthesis of organic fine chemicals. A few boron-containing organic pharmaceuticals are used or are in study, natural boron is composed of two stable isotopes, one of which has a number of uses as a neutron-capturing agent. In biology, borates have low toxicity in mammals, but are toxic to arthropods and are used as insecticides. Boric acid is mildly antimicrobial, and several natural boron-containing organic antibiotics are known, small amounts of boron compounds play a strengthening role in the cell walls of all plants, making boron a necessary plant nutrient. Boron is involved in the metabolism of calcium in both plants and animals and it is considered an essential nutrient for humans, and boron deficiency is implicated in osteoporosis. The word boron was coined from borax, the mineral from which it was isolated, by analogy with carbon, marco Polo brought some glazes back to Italy in the 13th century. Agricola, around 1600, reports the use of borax as a flux in metallurgy, in 1777, boric acid was recognized in the hot springs near Florence, Italy, and became known as sal sedativum, with primarily medical uses. The rare mineral is called sassolite, which is found at Sasso, Sasso was the main source of European borax from 1827 to 1872, when American sources replaced it. Boron compounds were relatively rarely used until the late 1800s when Francis Marion Smiths Pacific Coast Borax Company first popularized and produced them in volume at low cost
Boron
–
β-rhombohedral boron (most thermodynamically stable allotrope)
Boron
–
Sassolite.
Boron
–
Boron chunks
Boron
–
A fragment of ulexite
9.
Carbon
–
Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon also has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature. Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
Carbon
–
Graphite (left) and diamond (right), the two most well-known allotropes of carbon
Carbon
–
Spectral lines of carbon
Carbon
–
A large sample of glassy carbon.
Carbon
–
Graphite ore
10.
Nitrogen
–
Nitrogen is a chemical element with symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772, although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. Nitrogen is the lightest member of group 15 of the periodic table, the name comes from the Greek πνίγειν to choke, directly referencing nitrogens asphyxiating properties. It is an element in the universe, estimated at about seventh in total abundance in the Milky Way. At standard temperature and pressure, two atoms of the element bind to form dinitrogen, a colourless and odorless diatomic gas with the formula N2, dinitrogen forms about 78% of Earths atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids, in the nucleic acids, the human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air, into the biosphere and organic compounds, many industrially important compounds, such as ammonia, nitric acid, organic nitrates, and cyanides, contain nitrogen. The extremely strong bond in elemental nitrogen, the second strongest bond in any diatomic molecule. Synthetically produced ammonia and nitrates are key industrial fertilisers, and fertiliser nitrates are key pollutants in the eutrophication of water systems. Apart from its use in fertilisers and energy-stores, nitrogen is a constituent of organic compounds as diverse as Kevlar used in high-strength fabric, Nitrogen is a constituent of every major pharmacological drug class, including antibiotics. Many notable nitrogen-containing drugs, such as the caffeine and morphine or the synthetic amphetamines. Nitrogen compounds have a long history, ammonium chloride having been known to Herodotus. They were well known by the Middle Ages, alchemists knew nitric acid as aqua fortis, as well as other nitrogen compounds such as ammonium salts and nitrate salts. The mixture of nitric and hydrochloric acids was known as aqua regia, celebrated for its ability to dissolve gold, the discovery of nitrogen is attributed to the Scottish physician Daniel Rutherford in 1772, who called it noxious air. Though he did not recognise it as a different chemical substance, he clearly distinguished it from Joseph Blacks fixed air. The fact that there was a component of air that does not support combustion was clear to Rutherford, Nitrogen was also studied at about the same time by Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley, who referred to it as burnt air or phlogisticated air. Nitrogen gas was inert enough that Antoine Lavoisier referred to it as air or azote, from the Greek word άζωτικός. In an atmosphere of nitrogen, animals died and flames were extinguished
Nitrogen
–
Liquid nitrogen
Nitrogen
–
Spectral lines of nitrogen
Nitrogen
–
Nitrogen discharge (spectrum) tube
Nitrogen
–
Table tennis ball made from nitrocellulose.
11.
Oxygen
–
Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the group on the periodic table and is a highly reactive nonmetal. By mass, oxygen is the third-most abundant element in the universe, after hydrogen, at standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. This is an important part of the atmosphere and diatomic oxygen gas constitutes 20. 8% of the Earths atmosphere, additionally, as oxides the element makes up almost half of the Earths crust. Most of the mass of living organisms is oxygen as a component of water, conversely, oxygen is continuously replenished by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide. Oxygen is too reactive to remain a free element in air without being continuously replenished by the photosynthetic action of living organisms. Another form of oxygen, ozone, strongly absorbs ultraviolet UVB radiation, but ozone is a pollutant near the surface where it is a by-product of smog. At low earth orbit altitudes, sufficient atomic oxygen is present to cause corrosion of spacecraft, the name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle, Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philos work by observing that a portion of air is consumed during combustion and respiration, Oxygen was discovered by the Polish alchemist Sendivogius, who considered it the philosophers stone. In the late 17th century, Robert Boyle proved that air is necessary for combustion, English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. From this he surmised that nitroaereus is consumed in both respiration and combustion, Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract De respiratione. Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher, one part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the combustion products
Oxygen
–
Spectral lines of oxygen
Oxygen
Oxygen
–
A trickle of liquid oxygen is deflected by a magnetic field, illustrating its paramagnetic property
Oxygen
–
Oxygen discharge (spectrum) tube. The green color is similar to the color of an
"aurora borealis"
12.
Fluorine
–
Fluorine is a chemical element with symbol F and atomic number 9. It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions, as the most electronegative element, it is extremely reactive, almost all other elements, including some noble gases, form compounds with fluorine. Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance, proposed as an element in 1810, fluorine proved difficult and dangerous to separate from its compounds, and several early experimenters died or sustained injuries from their attempts. Only in 1886 did French chemist Henri Moissan isolate elemental fluorine using low-temperature electrolysis, industrial production of fluorine gas for uranium enrichment, its largest application, began during the Manhattan Project in World War II. Owing to the expense of refining pure fluorine, most commercial applications use fluorine compounds, the rest of the fluorite is converted into corrosive hydrogen fluoride en route to various organic fluorides, or into cryolite which plays a key role in aluminium refining. Organic fluorides have very high chemical and thermal stability, their uses are as refrigerants, electrical insulation and cookware. Pharmaceuticals such as atorvastatin and fluoxetine also contain fluorine, and the fluoride ion inhibits dental cavities, global fluorochemical sales amount to more than US$15 billion a year. Fluorocarbon gases are generally greenhouse gases with global-warming potentials 100 to 20,000 times that of carbon dioxide, organofluorine compounds persist in the environment due to the strength of the carbon–fluorine bond. Fluorine has no metabolic role in mammals, a few plants synthesize organofluorine poisons that deter herbivores. Fluorine atoms have nine electrons, one fewer than neon, and electron configuration 1s22s22p5, the outer electrons are ineffective at nuclear shielding, and experience a high effective nuclear charge of 9 −2 =7, this affects the atoms physical properties. Fluorines first ionization energy is third-highest among all elements, behind helium and neon and it also has a high electron affinity, second only to chlorine, and tends to capture an electron to become isoelectronic with the noble gas neon, it has the highest electronegativity of any element. Fluorine atoms have a small covalent radius of around 60 picometers, similar to those of its period neighbors oxygen, conversely, bonds to other atoms are very strong because of fluorines high electronegativity. Unreactive substances like powdered steel, glass fragments, and asbestos fibers react quickly with cold fluorine gas, wood, reactions of elemental fluorine with metals require varying conditions. Some solid nonmetals react vigorously in liquid air temperature fluorine, hydrogen sulfide and sulfur dioxide combine readily with fluorine, the latter sometimes explosively, sulfuric acid exhibits much less activity, requiring elevated temperatures. Hydrogen, like some of the metals, reacts explosively with fluorine. Carbon, as black, reacts at room temperature to yield fluoromethane. Graphite combines with fluorine above 400 °C to produce non-stoichiometric carbon monofluoride, higher temperatures generate gaseous fluorocarbons, heavier halogens react readily with fluorine as does the noble gas radon, of the other noble gases, only xenon and krypton react, and only under special conditions. At room temperature, fluorine is a gas of diatomic molecules and it has a characteristic pungent odor detectable at 20 ppb
Fluorine
–
Liquid fluorine at
cryogenic temperatures
Fluorine
–
Major fluorine-containing minerals
Fluorine
Fluorine
13.
Neon
–
Neon is a chemical element with symbol Ne and atomic number 10 and is a noble gas. Neon is a colorless, odorless, inert gas under standard conditions. It was discovered in 1898 as one of the three residual rare inert elements remaining in dry air, after nitrogen, oxygen, argon and carbon dioxide were removed. Neon was the second of three rare gases to be discovered, and was immediately recognized as a new element from its bright red emission spectrum. The name neon is derived from the Greek word, νέον, neuter singular form of νέος, Neon is chemically inert and forms no uncharged chemical compounds. The compounds of neon include ionic molecules, molecules held together by van der Waals forces and clathrates, during cosmic nucleogenesis of the elements, large amounts of neon are built up from the alpha-capture fusion process in stars. Although neon is a common element in the universe and solar system. It composes about 18.2 ppm of air by volume, the reason for neons relative scarcity on Earth and the inner planets is that neon is highly volatile and forms no compounds to fix it to solids. As a result, it escaped from the planetesimals under the warmth of the newly ignited Sun in the early Solar System, even the atmosphere of Jupiter is somewhat depleted of neon, presumably for this reason. It is also lighter than air, causing it to escape even from Earths atmosphere, Neon gives a distinct reddish-orange glow when used in low-voltage neon glow lamps, high-voltage discharge tubes and neon advertising signs. The red emission line from neon also causes the well known red light of helium–neon lasers, Neon is used in some plasma tube and refrigerant applications but has few other commercial uses. It is commercially extracted by the distillation of liquid air. Since air is the source, it is considerably more expensive than helium. Neon, was discovered in 1898 by the British chemists Sir William Ramsay, Neon was discovered when Ramsay chilled a sample of air until it became a liquid, then warmed the liquid and captured the gases as they boiled off. The gases nitrogen, oxygen, and argon had been identified, first to be identified was krypton. The next, after krypton had been removed, was a gas which gave a brilliant red light under spectroscopic discharge and this gas, identified in June, was named neon, the Greek analogue of novum, suggested by Ramsays son. A second gas was reported along with neon, having approximately the same density as argon but with a different spectrum – Ramsay. However, subsequent spectroscopic analysis revealed it to be contaminated with carbon monoxide
Neon
–
Neon, 10 Ne
Neon
–
Spectral lines of neon in the visible region
Neon
–
Neon
gas-discharge lamps forming the symbol for neon "Ne"
Neon
–
The first evidence for isotopes of a stable element was provided in 1913 by experiments on neon plasma. In the bottom right corner of
J. J. Thomson 's photographic plate are the separate impact marks for the two isotopes neon-20 and neon-22.
14.
Sodium
–
Sodium is a chemical element with symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal, Sodium is an alkali metal, being in group 1 of the periodic table, because it has a single electron in its outer shell that it readily donates, creating a positively charged atom—the Na+ cation. Its only stable isotope is 23Na, the free metal does not occur in nature, but must be prepared from compounds. Sodium is the sixth most abundant element in the Earths crust, Sodium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Among many other useful compounds, sodium hydroxide is used in soap manufacture, and sodium chloride is a de-icing agent. Sodium is an element for all animals and some plants. Sodium ions are the major cation in the fluid and as such are the major contributor to the ECF osmotic pressure. Loss of water from the ECF compartment increases the sodium concentration, isotonic loss of water and sodium from the ECF compartment decreases the size of that compartment in a condition called ECF hypovolemia. In nerve cells, the charge across the cell membrane enables transmission of the nerve impulse—an action potential—when the charge is dissipated. The melting and boiling points of sodium are lower than those of lithium but higher than those of the alkali metals potassium, rubidium. All of these high-pressure allotropes are insulators and electrides.3 nm, spin-orbit interactions involving the electron in the 3p orbital split the D line into two, at 589.0 and 589.6 nm, hyperfine structures involving both orbitals cause many more lines. Twenty isotopes of sodium are known, but only 23Na is stable, 23Na is created in the carbon-burning process in stars by fusing two carbon atoms together, this requires temperatures above 600 megakelvins and a star of at least three solar masses. Two nuclear isomers have been discovered, the one being 24mNa with a half-life of around 20.2 milliseconds. Sodium atoms have 11 electrons, one more than the stable configuration of the noble gas neon. This process requires so little energy that sodium is oxidized by giving up its 11th electron. In contrast, the ionization energy is very high, because the 10th electron is closer to the nucleus than the 11th electron. As a result, sodium usually forms ionic compounds involving the Na+ cation, the most common oxidation state for sodium is +1. It is generally less reactive than potassium and more reactive than lithium, Sodium metal is highly reducing, with the reduction of sodium ions requiring −2.71 volts, though potassium and lithium have even more negative potentials
Sodium
–
Sodium, 11 Na
Sodium
–
Spectral lines of sodium
Sodium
–
Emission spectrum for sodium, showing the
D line.
Sodium
–
A positive
flame test for sodium has a bright yellow color.
15.
Magnesium
–
Magnesium is a chemical element with symbol Mg and atomic number 12. Magnesium is the ninth most abundant element in the universe and it is produced in large, aging stars from the sequential addition of three helium nuclei to a carbon nucleus. When such stars explode as supernovas, much of the magnesium is expelled into the medium where it may recycle into new star systems. Magnesium is the eighth most abundant element in the Earths crust and the fourth most common element in the Earth, making up 13% of the planets mass and it is the third most abundant element dissolved in seawater, after sodium and chlorine. Magnesium occurs naturally only in combination with elements, where it invariably has a +2 oxidation state. The free element can be produced artificially, and is highly reactive, the free metal burns with a characteristic brilliant-white light. The metal is now obtained mainly by electrolysis of magnesium salts obtained from brine, Magnesium is less dense than aluminium, and the alloy is prized for its combination of lightness and strength. Magnesium is the eleventh most abundant element by mass in the body and is essential to all cells. Magnesium ions interact with polyphosphate compounds such as ATP, DNA, hundreds of enzymes require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives, antacids, elemental magnesium is a gray-white lightweight metal, two-thirds the density of aluminium. Magnesium has the lowest melting and the lowest boiling point 1,363 K of all the alkaline earth metals, Magnesium reacts with water at room temperature, though it reacts much more slowly than calcium, a similar group 2 metal. When submerged in water, hydrogen bubbles form slowly on the surface of the metal—though, if powdered, the reaction occurs faster with higher temperatures. Magnesiums reversible reaction with water can be harnessed to store energy, Magnesium also reacts exothermically with most acids such as hydrochloric acid, producing the metal chloride and hydrogen gas, similar to the HCl reaction with aluminium, zinc, and many other metals. Magnesium is highly flammable, especially when powdered or shaved into thin strips, flame temperatures of magnesium and magnesium alloys can reach 3,100 °C, although flame height above the burning metal is usually less than 300 mm. Once ignited, such fires are difficult to extinguish, with combustion continuing in nitrogen, carbon dioxide, Magnesium may also be used as an igniter for thermite, a mixture of aluminium and iron oxide powder that ignites only at a very high temperature. When burning in air, magnesium produces a light that includes strong ultraviolet wavelengths. Magnesium powder was used for illumination in the early days of photography. Later, magnesium filament was used in electrically ignited single-use photography flashbulbs, Magnesium powder is used in fireworks and marine flares where a brilliant white light is required
Magnesium
–
Magnesium, 12 Mg
Magnesium
–
Spectral lines of magnesium
Magnesium
–
Magnesium sheets and ingots
Magnesium
–
An unusual application of magnesium as an
illumination source while
wakeskating in 1931
16.
Aluminium
–
Aluminium or aluminum is a chemical element in the boron group with symbol Al and atomic number 13. It is a silvery-white, soft, nonmagnetic, ductile metal, Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is combined in over 270 different minerals. The chief ore of aluminium is bauxite, Aluminium is remarkable for the metals low density and its ability to resist corrosion through the phenomenon of passivation. Aluminium and its alloys are vital to the industry and important in transportation and structures, such as building facades. The oxides and sulfates are the most useful compounds of aluminium, despite its prevalence in the environment, no known form of life uses aluminium salts metabolically, but aluminium is well tolerated by plants and animals. Because of these salts abundance, the potential for a role for them is of continuing interest. Aluminium is a soft, durable, lightweight, ductile. It is nonmagnetic and does not easily ignite, a fresh film of aluminium serves as a good reflector of visible light and an excellent reflector of medium and far infrared radiation. The yield strength of aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium has about one-third the density and stiffness of steel and it is easily machined, cast, drawn and extruded. Aluminium atoms are arranged in a cubic structure. Aluminium has an energy of approximately 200 mJ/m2. Aluminium is a thermal and electrical conductor, having 59% the conductivity of copper. Aluminium is capable of superconductivity, with a critical temperature of 1.2 kelvin. Aluminium is the most common material for the fabrication of superconducting qubits, the strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper. This corrosion resistance is reduced by aqueous salts, particularly in the presence of dissimilar metals. In highly acidic solutions, aluminium reacts with water to form hydrogen, primarily because it is corroded by dissolved chlorides, such as common sodium chloride, household plumbing is never made from aluminium
Aluminium
–
Aluminium, 13 Al
Aluminium
–
Spectral lines of aluminium
Aluminium
–
"
Red mud " storage facility in
Stade,
Germany. The aluminium industry generates about 70 million tons of this waste annually.
Aluminium
–
Bauxite, a major aluminium ore. The red-brown color is due to the presence of
iron minerals.
17.
Silicon
–
Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a metallic luster. It is a member of group 14 in the table, along with carbon above it and germanium, tin, lead. It is not very reactive, although more reactive than germanium, Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earths crust. It is most widely distributed in dusts, sands, planetoids, over 90% of the Earths crust is composed of silicate minerals, making silicon the second most abundant element in the Earths crust after oxygen. Most silicon is used commercially without being separated, and often with little processing of the natural minerals, such use includes industrial construction with clays, silica sand, and stone. Silicate is used in Portland cement for mortar and stucco, and mixed with sand and gravel to make concrete for walkways, foundations. Silicates are used in whiteware ceramics such as porcelain, and in traditional quartz-based soda-lime glass, Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics. Elemental silicon also has an impact on the modern world economy. Most free silicon is used in the refining, aluminium-casting. Silicon is the basis of the widely used synthetic polymers called silicones, Silicon is an essential element in biology, although only tiny traces are required by animals. However, various sea sponges and microorganisms, such as diatoms and radiolaria, silica is deposited in many plant tissues, such as in the bark and wood of Chrysobalanaceae and the silica cells and silicified trichomes of Cannabis sativa, horsetails and many grasses. Silicon is a solid at room temperature, with a point of 1,414 °C. Like water, it has a density in a liquid state than in a solid state and it expands when it freezes. With a relatively high conductivity of 149 W·m−1·K−1, silicon conducts heat well. In its crystalline form, pure silicon has a gray color, like germanium, silicon is rather strong, very brittle, and prone to chipping. Silicon, like carbon and germanium, crystallizes in a cubic crystal structure with a lattice spacing of 0.5430710 nm. The outer electron orbital of silicon, like that of carbon, has four valence electrons, the 1s, 2s, 2p and 3s subshells are completely filled while the 3p subshell contains two electrons out of a possible six
Silicon
–
Silicon, 14 Si
Silicon
–
Spectral lines of silicon
Silicon
–
Silicon powder
Silicon
–
Quartz crystal cluster from
Tibet. The naturally occurring mineral is a network solid with the formula SiO 2.
18.
Phosphorus
–
Phosphorus is a chemical element with symbol P and atomic number 15. As an element, phosphorus exists in two major forms—white phosphorus and red phosphorus—but because it is reactive, phosphorus is never found as a free element on Earth. At 0. 099%, phosphorus is the most abundant pnictogen in the Earths crust, with few exceptions, minerals containing phosphorus are in the maximally oxidised state as inorganic phosphate rocks. The glow of phosphorus itself originates from oxidation of the white phosphorus — a process now termed chemiluminescence, together with nitrogen, arsenic, antimony, and bismuth, phosphorus is classified as a pnictogen. Phosphates are a component of DNA, RNA, ATP, and the phospholipids, demonstrating the link between phosphorus and life, elemental phosphorus was first isolated from human urine, and bone ash was an important early phosphate source. Phosphate mines contain fossils, especially marine fossils, because phosphate is present in the deposits of animal remains. Low phosphate levels are an important limit to growth in aquatic systems. The vast majority of compounds produced are consumed as fertilisers. Phosphate is needed to replace the phosphorus that plants remove from the soil, other applications include the role of organophosphorus compounds in detergents, pesticides, and nerve agents. Phosphorus exists as several forms that exhibit different properties. The two most common allotropes are white phosphorus and red phosphorus, from the perspective of applications and chemical literature, the most important form of elemental phosphorus is white phosphorus, often abbreviated as WP. It is a soft and waxy solid consists of tetrahedral P4 molecules. This P4 tetrahedron is also present in liquid and gaseous phosphorus up to the temperature of 800 °C when it starts decomposing to P2 molecules, White phosphorus exists in two crystalline forms, α and β. At room temperature, the α-form is stable, which is common and it has cubic crystal structure and at 195.2 K, it transforms into β-form. These forms differ in terms of the orientations of the constituent P4 tetrahedra. White phosphorus is the least stable, the most reactive, the most volatile, the least dense, White phosphorus gradually changes to red phosphorus. This transformation is accelerated by light and heat, and samples of white phosphorus almost always some red phosphorus. For this reason, white phosphorus that is aged or otherwise impure is also called yellow phosphorus, when exposed to oxygen, white phosphorus glows in the dark with a very faint tinge of green and blue
Phosphorus
–
waxy white (yellow cut), red (granules centre left, chunk centre right), and violet phosphorus
Phosphorus
–
P 4 molecule
Phosphorus
–
White phosphorus
Phosphorus
–
Crystal structure of red phosphorus
19.
Sulfur
–
Sulfur or sulphur is a chemical element with symbol S and atomic number 16. It is abundant, multivalent, and nonmetallic, under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a yellow crystalline solid at room temperature. Chemically, sulfur reacts with all elements except for gold, platinum, iridium, tellurium, though sometimes found in pure, native form, sulfur usually occurs as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient times, being mentioned for its uses in ancient India, ancient Greece, China, in the Bible, sulfur is called brimstone. Today, almost all elemental sulfur is produced as a byproduct of removing sulfur-containing contaminants from natural gas, the greatest commercial use of the element is the production of sulfuric acid for sulfate and phosphate fertilizers, and other chemical processes. The element sulfur is used in matches, insecticides, and fungicides, many sulfur compounds are odoriferous, and the smells of odorized natural gas, skunk scent, grapefruit, and garlic are due to organosulfur compounds. Hydrogen sulfide gives the characteristic odor to rotting eggs and other biological processes, sulfur is an essential element for all life, but almost always in the form of organosulfur compounds or metal sulfides. Three amino acids and two vitamins are organosulfur compounds, many cofactors also contain sulfur including glutathione and thioredoxin and iron–sulfur proteins. Disulfides, S–S bonds, confer mechanical strength and insolubility of the keratin, found in outer skin, hair. Sulfur is one of the chemical elements needed for biochemical functioning and is an elemental macronutrient for all organisms. Sulfur is derived from the Latin word sulpur, which was Hellenized to sulphur, the spelling sulfur appears toward the end of the Classical period. In 12th-century Anglo-French, it was sulfre, in the 14th century the Latin ph was restored, for sulphre, the parallel f~ph spellings continued in Britain until the 19th century, when the word was standardized as sulphur. Sulfur was the form chosen in the United States, whereas Canada uses both, the IUPAC adopted the spelling sulfur in 1990, as did the Nomenclature Committee of the Royal Society of Chemistry in 1992, restoring the spelling sulfur to Britain. Sulfur forms polyatomic molecules with different chemical formulas, the best-known allotrope being octasulfur, cyclo-S8. The point group of cyclo-S8 is D4d and its dipole moment is 0 D. Octasulfur is a soft, bright-yellow solid that is odorless and it melts at 115.21 °C, boils at 444.6 °C and sublimes easily. At 95.2 °C, below its melting temperature, cyclo-octasulfur changes from α-octasulfur to the β-polymorph, the structure of the S8 ring is virtually unchanged by this phase change, which affects the intermolecular interactions. At higher temperatures, the viscosity decreases as depolymerization occurs, molten sulfur assumes a dark red color above 200 °C
Sulfur
–
Sulfur, 16 S
Sulfur
–
Spectral lines of sulfur
Sulfur
–
Nearly exhausted sulfur vat from which railroad cars are loaded, Freeport Sulphur Co., Hoskins Mound, Texas (1943).
Sulfur
–
Most of the yellow and orange hues of
Io are due to elemental sulfur and sulfur compounds, produced by active volcanoes.
20.
Chlorine
–
Chlorine is a chemical element with symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the table and its properties are mostly intermediate between them. Chlorine is a gas at room temperature. It is an extremely reactive element and a strong oxidising agent, among the elements, it has the highest electron affinity, the most common compound of chlorine, sodium chloride, has been known since ancient times. Around 1630, chlorine gas was first synthesised in a chemical reaction, Carl Wilhelm Scheele wrote a description of chlorine gas in 1774, supposing it to be an oxide of a new element. In 1809, chemists suggested that the gas might be an element, and this was confirmed by Sir Humphry Davy in 1810. Because of its reactivity, all chlorine in the Earths crust is in the form of ionic chloride compounds. It is the second-most abundant halogen and twenty-first most abundant chemical element in Earths crust and these crustal deposits are nevertheless dwarfed by the huge reserves of chloride in seawater. Elemental chlorine is produced from brine by electrolysis. The high oxidising potential of chlorine led to the development of commercial bleaches and disinfectants. As a common disinfectant, elemental chlorine and chlorine-generating compounds are used directly in swimming pools to keep them clean. Elemental chlorine at high concentrations is extremely dangerous and poisonous for all living organisms, in the form of chloride ions, chlorine is necessary to all known species of life. Other types of compounds are rare in living organisms. In the upper atmosphere, chlorine-containing organic molecules such as chlorofluorocarbons have been implicated in ozone depletion, small quantities of elemental chlorine are generated by oxidation of chloride to hypochlorite in neutrophils as part of the immune response against bacteria. Its importance in food was very well known in antiquity and was sometimes used as payment for services for Roman generals. Around 1630, chlorine was recognized as a gas by the Flemish chemist, the element was first studied in detail in 1774 by Swedish chemist Carl Wilhelm Scheele, and he is credited with the discovery. He called it dephlogisticated muriatic acid air since it is a gas and he failed to establish chlorine as an element, mistakenly thinking that it was the oxide obtained from the hydrochloric acid. He named the new element within this oxide as muriaticum, in 1809, Joseph Louis Gay-Lussac and Louis-Jacques Thénard tried to decompose dephlogisticated muriatic acid air by reacting it with charcoal to release the free element muriaticum
Chlorine
–
A glass container filled with chlorine gas
Chlorine
–
Chlorine, liquefied under a pressure of 7.4 bar at room temperature, displayed in a quartz ampule embedded in
acrylic glass.
Chlorine
–
Carl Wilhelm Scheele
Chlorine
–
Liquid chlorine analysis
21.
Argon
–
Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the table and is a noble gas. Argon is the third-most abundant gas in the Earths atmosphere, at 0. 934% and it is more than twice as abundant as water vapor,23 times as abundant as carbon dioxide, and more than 500 times as abundant as neon. Argon is the most abundant noble gas in Earths crust, comprising 0. 00015% of the crust, nearly all of the argon in Earths atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earths crust. In the universe, argon-36 is by far the most common argon isotope, the name argon is derived from the Greek word ἀργόν, neuter singular form of ἀργός meaning lazy or inactive, as a reference to the fact that the element undergoes almost no chemical reactions. The complete octet in the atomic shell makes argon stable. Its triple point temperature of 83.8058 K is a fixed point in the International Temperature Scale of 1990. Argon is produced industrially by the distillation of liquid air. Argon is also used in incandescent, fluorescent lighting, and other gas-discharge tubes, Argon makes a distinctive blue-green gas laser. Argon is also used in fluorescent glow starters, Argon has approximately the same solubility in water as oxygen and is 2.5 times more soluble in water than nitrogen. Argon is colorless, odorless, nonflammable and nontoxic as a solid, liquid or gas, Argon is chemically inert under most conditions and forms no confirmed stable compounds at room temperature. Although argon is a gas, it can form some compounds under extreme conditions. Argon fluorohydride, a compound of argon with fluorine and hydrogen that is stable below 17 K, has been demonstrated. Although the neutral ground-state chemical compounds of argon are presently limited to HArF, ions, such as ArH+, and excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more argon compounds that should be stable but have not yet been synthesized, Argon was suspected to be a component of air by Henry Cavendish in 1785. Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water and they had determined that nitrogen produced from chemical compounds was 0. 5% lighter than nitrogen from the atmosphere. The difference was slight, but it was important enough to attract their attention for many months and they concluded that there was another gas in the air mixed in with the nitrogen. Argon was also encountered in 1882 through independent research of H. F. Newall, each observed new lines in the color spectrum of air that did not match known elements
Argon
–
Argon, 18 Ar
Argon
–
A small piece of rapidly melting solid argon.
Argon
–
Cylinders containing argon gas for use in extinguishing fire without damaging server equipment
Argon
–
A sample of
caesium is packed under argon to avoid reactions with air
22.
Potassium
–
Potassium is a chemical element with symbol K and atomic number 19. It was first isolated from potash, the ashes of plants, in the periodic table, potassium is one of the alkali metals. Potassium in nature only in ionic salts. It is found dissolved in sea water, and is part of many minerals, naturally occurring potassium is composed of three isotopes, of which 40K is radioactive. Traces of 40K are found in all potassium, and it is the most common radioisotope in the human body, Potassium is chemically very similar to sodium, the previous element in Group 1 of the periodic table. They have a similar energy, which allows for each atom to give up its sole outer electron. That they are different elements combine with the same anions to make similar salts was suspected in 1702. Most industrial applications of potassium exploit the high solubility in water of potassium compounds, heavy crop production rapidly depletes the soil of potassium, and this can be remedied with agricultural fertilizers containing potassium, accounting for 95% of global potassium chemical production. Potassium ions are necessary for the function of all living cells, fresh fruits and vegetables are good dietary sources of potassium. Potassium is the second least dense metal after lithium and it is a soft solid with a low melting point, and can be easily cut with a knife. Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately on exposure to air, in a flame test, potassium and its compounds emit a lilac color with a peak emission wavelength of 766.5 nanometers. Neutral potassium atoms have 19 electrons, one more than the stable configuration of the noble gas argon. This process requires so little energy that potassium is readily oxidized by atmospheric oxygen, in contrast, the second ionization energy is very high, because removal of two electrons breaks the stable noble gas electronic configuration. Potassium therefore does not readily form compounds with the state of +2 or higher. Potassium is an active metal that reacts violently with oxygen in water. With oxygen it forms potassium peroxide, and with water potassium forms potassium hydroxide, the reaction of potassium with water is dangerous because of its violent exothermic character and the production of hydrogen gas. Hydrogen reacts again with atmospheric oxygen, producing water, which reacts with the remaining potassium and this reaction requires only traces of water, because of this, potassium and the liquid sodium-potassium — NaK — are potent desiccants that can be used to dry solvents prior to distillation. Because of the sensitivity of potassium to water and air, reactions with other elements are only in an inert atmosphere such as argon gas using air-free techniques
Potassium
–
Potassium pearls under paraffin oil. The large pearl measures 0.5 cm.
Potassium
–
Spectral lines of potassium
Potassium
–
Potassium in
feldspar
Potassium
–
Humphry Davy
23.
Calcium
–
Calcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft grayish-yellow alkaline earth metal, fifth-most-abundant element by mass in the Earths crust, the ion Ca2+ is also the fifth-most-abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate. Free calcium metal is too reactive to occur in nature, Calcium is produced in supernova nucleosynthesis. Calcium is a trace element in living organisms. It is the most abundant metal by mass in animals, and it is an important constituent of bone, teeth. In cell biology, the movement of the calcium ion into, Calcium carbonate and calcium citrate are often taken as dietary supplements. Calcium is on the World Health Organizations List of Essential Medicines, Calcium has a wide variety of applications, almost all of which are associated with calcium compounds and salts. Calcium metal is used as a deoxidizer, desulfurizer, and decarbonizer for production of ferrous and nonferrous alloys. In steelmaking and production of iron, Ca reacts with oxygen, Calcium carbonate is used in manufacturing cement and mortar, lime, limestone and aids in production in the glass industry. It also has chemical and optical uses as mineral specimens in toothpastes, Calcium hydroxide solution is used to detect the presence of carbon dioxide in a gas sample bubbled through a solution. The solution turns cloudy where CO2 is present, Calcium arsenate is used in insecticides. Calcium carbide is used to make acetylene gas and various plastics, Calcium chloride is used in ice removal and dust control on dirt roads, as a conditioner for concrete, as an additive in canned tomatoes, and to provide body for automobile tires. Calcium citrate is used as a food preservative, Calcium cyclamate is used as a sweetening agent in several countries. In the United States, it has been outlawed as a suspected carcinogen, Calcium gluconate is used as a food additive and in vitamin pills. Calcium hypochlorite is used as a swimming pool disinfectant, as an agent, as an ingredient in deodorant. Calcium permanganate is used in rocket propellant, textile production, as a water sterilizing agent. Calcium phosphate is used as a supplement for animal feed, fertilizer, in production for dough and yeast products, in the manufacture of glass. Calcium phosphide is used in fireworks, rodenticide, torpedoes, Calcium sulfate is used as common blackboard chalk, as well as, in its hemihydrate form, Plaster of Paris
Calcium
–
Calcium, 20 Ca
Calcium
–
Travertine terraces
Pamukkale, Turkey
Calcium
–
'Ain Ghazal figure
Calcium
–
500 milligram calcium supplements made from
calcium carbonate
24.
Scandium
–
Scandium is a chemical element with symbol Sc and atomic number 21. A silvery-white metallic d-block element, it has historically been classified as a rare earth element, together with yttrium. It was discovered in 1879 by spectral analysis of the minerals euxenite and gadolinite from Scandinavia, Scandium is present in most of the deposits of rare earth and uranium compounds, but it is extracted from these ores in only a few mines worldwide. Because of the low availability and the difficulties in the preparation of metallic scandium, the positive effects of scandium on aluminium alloys were discovered in the 1970s, and its use in such alloys remains its only major application. The global trade of scandium oxide is about 10 tonnes per year, the properties of scandium compounds are intermediate between those of aluminium and yttrium. A diagonal relationship exists between the behavior of magnesium and scandium, just as there is between beryllium and aluminium, in the chemical compounds of the elements in group 3, the predominant oxidation state is +3. Scandium is a metal with a silvery appearance. It develops a slightly yellowish or pinkish cast when oxidized by air and it is susceptible to weathering and dissolves slowly in most dilute acids. It does not react with a 1,1 mixture of acid and 48% hydrofluoric acid. Scandium turnings ignite in air with a brilliant yellow flame to form scandium oxide, in nature, scandium is found exclusively as the isotope 45Sc, which has a nuclear spin of 7/2. Thirteen radioisotopes have been characterized with the most stable being 46Sc, which has a half-life of 83.8 days, 47Sc,3.35 days, the positron emitter 44Sc,4 h, and 48Sc,43.7 hours. All of the radioactive isotopes have half-lives less than 4 hours. This element also has five meta states, with the most stable being 44mSc, the isotopes of scandium range from 36Sc to 60Sc. The primary decay mode at masses lower than the stable isotope, 45Sc, is electron capture. The primary decay products at atomic weights below 45Sc are calcium isotopes, in Earths crust, scandium is not rare. Estimates vary from 18 to 25 ppm, which is comparable to the abundance of cobalt, Scandium is only the 50th most common element on Earth, but it is the 23rd most common element in the Sun. However, scandium is distributed sparsely and occurs in trace amounts in many minerals, rare minerals from Scandinavia and Madagascar such as thortveitite, euxenite, and gadolinite are the only known concentrated sources of this element. Thortveitite can contain up to 45% of scandium in the form of scandium oxide, the stable form of scandium is created in supernovas via the r-process
Scandium
–
Scandium, 21 Sc
Scandium
–
Parts of the
MiG-29 are made from Al-Sc alloy.
25.
Titanium
–
Titanium is a chemical element with symbol Ti and atomic number 22. It is a transition metal with a silver color, low density. Titanium is resistant to corrosion in sea water, aqua regia, titanium was discovered in Cornwall, Great Britain, by William Gregor in 1791, and it is named by Martin Heinrich Klaproth for the Titans of Greek mythology. The metal is extracted from its principal mineral ores by the Kroll, the most common compound, titanium dioxide, is a popular photocatalyst and is used in the manufacture of white pigments. Other compounds include titanium tetrachloride, a component of smoke screens and catalysts, and titanium trichloride, the two most useful properties of the metal are corrosion resistance and strength-to-density ratio, the highest of any metallic element. In its unalloyed condition, titanium is as strong as some steels, there are two allotropic forms and five naturally occurring isotopes of this element, 46Ti through 50Ti, with 48Ti being the most abundant. Although they have the number of valence electrons and are in the same group in the periodic table. As a metal, titanium is recognized for its high strength-to-weight ratio and it is a strong metal with low density that is quite ductile, lustrous, and metallic-white in color. The relatively high melting point makes it useful as a refractory metal and it is paramagnetic and has fairly low electrical and thermal conductivity. Commercial grades of titanium have ultimate tensile strength of about 434 MPa, equal to that of common, low-grade steel alloys, titanium is 60% denser than aluminium, but more than twice as strong as the most commonly used 6061-T6 aluminium alloy. Certain titanium alloys achieve tensile strengths of over 1400 MPa, however, titanium loses strength when heated above 430 °C. Titanium is not as hard as some grades of heat-treated steel, it is non-magnetic, machining requires precautions, because the material might gall unless sharp tools and proper cooling methods are used. Like steel structures, those made from titanium have a limit that guarantees longevity in some applications. The metal is an allotrope of an hexagonal α form that changes into a body-centered cubic β form at 882 °C. The specific heat of the α form increases dramatically as it is heated to this transition temperature but then falls, similar to zirconium and hafnium, an additional omega phase exists, which is thermodynamically stable at high pressures, but metastable at ambient pressures. This phase is usually hexagonal or trigonal and can be considered to be due to a soft longitudinal acoustic phonon of the β phase causing collapse of planes of atoms, like aluminium and magnesium, titanium metal and its alloys oxidize immediately upon exposure to air. Titanium readily reacts with oxygen at 1,200 °C in air and it is, however, slow to react with water and air at ambient temperatures because it forms a passive oxide coating that protects the bulk metal from further oxidation. When it first forms, this layer is only 1–2 nm thick but continues to grow slowly
Titanium
–
Titanium, 22 Ti
Titanium
–
Titanium(III) compounds are characteristically violet, illustrated by this aqueous solution of
titanium trichloride.
Titanium
–
Martin Heinrich Klaproth named titanium for the
Titans of
Greek mythology.
Titanium
–
Titanium sponge, made by the
Kroll process
26.
Vanadium
–
Vanadium is a chemical element with symbol V and atomic number 23. It is a hard, silvery grey, ductile, and malleable transition metal, the elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer stabilizes the free metal somewhat against further oxidation. Four years later, however, he was convinced by other scientists that erythronium was identical to chromium, both names were attributed to the wide range of colors found in vanadium compounds. Del Rios lead mineral was later renamed vanadinite for its vanadium content, in 1867 Henry Enfield Roscoe obtained the pure element. Vanadium occurs naturally in about 65 different minerals and in fossil fuel deposits and it is produced in China and Russia from steel smelter slag, other countries produce it either from the flue dust of heavy oil, or as a byproduct of uranium mining. It is mainly used to produce specialty steel alloys such as high-speed tool steels, the most important industrial vanadium compound, vanadium pentoxide, is used as a catalyst for the production of sulfuric acid. Large amounts of ions are found in a few organisms. The oxide and some salts of vanadium have moderate toxicity. Particularly in the ocean, vanadium is used by life forms as an active center of enzymes. Vanadium was discovered by Andrés Manuel del Río, a Spanish-Mexican mineralogist, Del Río extracted the element from a sample of Mexican brown lead ore, later named vanadinite. He found that its salts exhibit a variety of colors. Later, Del Río renamed the element erythronium because most of the salts turned red upon heating, Del Río accepted Collet-Descotils statement and retracted his claim. In 1831, the Swedish chemist Nils Gabriel Sefström rediscovered the element in a new oxide he found working with iron ores. Later that same year, Friedrich Wöhler confirmed del Ríos earlier work, Sefström chose a name beginning with V, which had not been assigned to any element yet. He called the element vanadium after Old Norse Vanadís, because of the many beautifully colored chemical compounds it produces, in 1831, the geologist George William Featherstonhaugh suggested that vanadium should be renamed rionium after del Río, but this suggestion was not followed. The isolation of vanadium metal proved difficult, in 1831, Berzelius reported the production of the metal, but Henry Enfield Roscoe showed that Berzelius had in fact produced the nitride, vanadium nitride. Roscoe eventually produced the metal in 1867 by reduction of chloride, VCl2. In 1927, pure vanadium was produced by reducing vanadium pentoxide with calcium, the first large-scale industrial use of vanadium was in the steel alloy chassis of the Ford Model T, inspired by French race cars
Vanadium
–
Vanadium, 23 V
Vanadium
–
The
Model T made use of vanadium steel in its
chassis.
Vanadium
–
High-purity (99.95%) vanadium cuboids,
ebeam remelted and macro-etched
Vanadium
–
From left: [V(H 2 O) 6] 2+ (lilac), [V(H 2 O) 6] 3+ (green), [VO(H 2 O) 5] 2+ (blue) and [VO(H 2 O) 5] 3+ (yellow).
27.
Chromium
–
Chromium is a chemical element with symbol Cr and atomic number 24. It is the first element in Group 6 and it is a steely-grey, lustrous, hard and brittle metal which takes a high polish, resists tarnishing, and has a high melting point. The name of the element is derived from the Greek word χρῶμα, chrōma, meaning color, Chromium metal is of high value for its high corrosion resistance and hardness. A major development was the discovery that steel could be highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. Stainless steel and chrome plating together comprise 85% of the commercial use, trivalent chromium ion is an essential nutrient in trace amounts in humans for insulin, sugar and lipid metabolism, although the issue is debated. While chromium metal and Cr ions are not considered toxic, hexavalent chromium is toxic and carcinogenic, abandoned chromium production sites often require environmental cleanup. Chromium is remarkable for its properties, it is the only elemental solid which shows antiferromagnetic ordering at room temperature. Above 38 °C, it changes to paramagnetic, Chromium metal left standing in air is passivated by oxidation, forming a thin, protective, surface layer. This layer is a structure only a few molecules thick. It is very dense, and prevents the diffusion of oxygen into the underlying metal and this is different from the oxide that forms on iron and carbon steel, through which elemental oxygen continues to migrate, reaching the underlying material to cause incessant rusting. Passivation can be enhanced by short contact with oxidizing acids like nitric acid, passivated chromium is stable against acids. Passivation can be removed with a reducing agent that destroys the protective oxide layer on the metal. Chromium metal treated in this way readily dissolves in weak acids, Chromium, unlike such metals as iron and nickel, does not suffer from hydrogen embrittlement. However, it suffer from nitrogen embrittlement, reacting with nitrogen from air. Chromium is the 22nd most abundant element in Earths crust with a concentration of 100 ppm. Chromium compounds are found in the environment from the erosion of chromium-containing rocks, Chromium is mined as chromite ore. About two-fifths of the ores and concentrates in the world are produced in South Africa, while Kazakhstan, India, Russia. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan, although rare, deposits of native chromium exist
Chromium
–
chromium crystals
Chromium
–
Crocoite (PbCrO 4)
Chromium
–
Chromite ore
Chromium
–
Chromium(III) chloride hexahydrate ([CrCl 2 (H 2 O) 4]Cl·2H 2 O)
28.
Manganese
–
Manganese is a chemical element with symbol Mn and atomic number 25. It is not found as an element in nature, it is often found in minerals in combination with iron. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels, by the mid-18th century, Swedish chemist Carl Wilhelm Scheele had used pyrolusite to produce chlorine. Scheele and others were aware that pyrolusite contained a new element, johan Gottlieb Gahn was the first to isolate an impure sample of manganese metal in 1774, which he did by reducing the dioxide with carbon. Manganese phosphating is used for rust and corrosion prevention on steel, ionized manganese is used industrially as pigments of various colors, which depend on the oxidation state of the ions. The permanganates of alkali and alkaline earth metals are powerful oxidizers, Manganese dioxide is used as the cathode material in zinc-carbon and alkaline batteries. In biology, manganese ions function as cofactors for a variety of enzymes with many functions. Manganese enzymes are essential in detoxification of superoxide free radicals in organisms that must deal with elemental oxygen. Manganese also functions in the complex of photosynthetic plants. The element is a trace mineral for all known living organisms but is a neurotoxin. In larger amounts, and apparently with far greater effectiveness through inhalation, Manganese is a silvery-gray metal that resembles iron. It is hard and very brittle, difficult to fuse, Manganese metal and its common ions are paramagnetic. Manganese tarnishes slowly in air and oxidizes like iron in water containing dissolved oxygen, naturally occurring manganese is composed of one stable isotope, 55Mn. Eighteen radioisotopes have been isolated and described, the most stable being 53Mn with a half-life of 3.7 million years, 54Mn with a half-life of 312.3 days, and 52Mn with a half-life of 5.591 days. All of the radioactive isotopes have half-lives of less than three hours, and the majority of less than one minute. Manganese also has three meta states, Manganese is part of the iron group of elements, which are thought to be synthesized in large stars shortly before the supernova explosion. 53Mn decays to 53Cr with a half-life of 3.7 million years, because of its relatively short half-life, 53Mn is relatively rare, produced by cosmic rays impact on iron. Manganese isotopic contents are combined with chromium isotopic contents and have found application in isotope geology
Manganese
–
Manganese, 25 Mn
Manganese
–
Electrolytically refined manganese chips and 1 cm 3 cube
Manganese
–
Manganese(II) chloride crystals – the pale pink color of Mn(II) salts is due to a spin-forbidden 3d transition.
Manganese
–
Aqueous solution of KMnO 4 illustrating the deep purple of Mn(VII) as it occurs in permanganate
29.
Iron
–
Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements, ruthenium and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron. Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is also the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, tissues, muscles, bone marrow, blood proteins, enzymes, ferritin, hemosiderin, and transport in plasma. The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have also been studied extensively
Iron
–
Iron, 26 Fe
Iron
–
Spectral lines of iron
Iron
–
Iron meteorites, similar in composition to the Earth's inner- and outer core
Iron
–
Hydrated
iron(III) chloride, also known as ferric chloride
30.
Cobalt
–
Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt is found in the Earths crust only in chemically combined form, the free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal. In 1735, such ores were found to be reducible to a new metal, today, some cobalt is produced specifically from various metallic-lustered ores, for example cobaltite, but the main source of the element is as a by-product of copper and nickel mining. The copper belt in the Democratic Republic of the Congo, Central African Republic, cobalt is primarily used in the preparation of magnetic, wear-resistant and high-strength alloys. The compounds, cobalt silicate and cobalt aluminate give a deep blue color to glass, ceramics, inks, paints. Cobalt occurs naturally as only one isotope, cobalt-59. Cobalt-60 is an important radioisotope, used as a radioactive tracer. Cobalt is the center of coenzymes called cobalamins, the most common example of which is vitamin B12. As such, it is a trace dietary mineral for all animals. Cobalt in inorganic form is also a micronutrient for bacteria, algae, cobalt is a ferromagnetic metal with a specific gravity of 8.9. The Curie temperature is 1,115 °C and the moment is 1. 6–1.7 Bohr magnetons per atom. Cobalt has a relative permeability two-thirds that of iron, metallic cobalt occurs as two crystallographic structures, hcp and fcc. The ideal transition temperature between the hcp and fcc structures is 450 °C, but in practice, the difference is so small that random intergrowth of the two is common. Cobalt is a weakly reducing metal that is protected from oxidation by an oxide film. It is attacked by halogens and sulfur, heating in oxygen produces Co3O4 which loses oxygen at 900 °C to give the monoxide CoO. The metal reacts with fluorine at 520 K to give CoF3, with chlorine, bromine and iodine and it does not react with hydrogen gas or nitrogen gas even when heated, but it does react with boron, carbon, phosphorus, arsenic and sulfur. At ordinary temperatures, it reacts slowly with mineral acids, and very slowly with moist, common oxidation states of cobalt include +2 and +3, although compounds with oxidation states ranging from −3 to +5 are also known. A common oxidation state for simple compounds is +2 and these salts form the pink-colored metal aquo complex 2+ in water
Cobalt
–
electrolytically refined cobalt chips
Cobalt
–
A block of
electrolytically refined cobalt (99.9% purity) cut from a large plate
Cobalt
–
Cobalt(II) chloride hexahydrate
Cobalt
–
Early Chinese blue and white porcelain, manufactured circa 1335
. doi:10.1086/344473.
