1.
Iron(II) oxide
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Iron oxide or ferrous oxide is the inorganic compound with the formula FeO. Its mineral form is known as wüstite, one of several iron oxides, it is a black-colored powder that is sometimes confused with rust, which consists of hydrated iron oxide. Iron oxide also refers to a family of related non-stoichiometric compounds, FeO can be prepared by the thermal decomposition of iron oxalate. FeC2O4 → FeO + CO2 + CO The procedure is conducted under an atmosphere to avoid the formation of ferric oxide. A similar procedure can also be used for the synthesis of manganous oxide, stoichiometric FeO can be prepared by heating Fe0. 95O with metallic iron at 770 °C and 36 kbar. Below 200 K there is a change to the structure which changes the symmetry to rhombohedral. Iron oxide makes up approximately 9% of the Earths mantle, within the mantle, it may be electrically conductive, which is a possible explanation for perturbations in Earths rotation not accounted for by accepted models of the mantles properties. Iron oxide is used as a pigment and it is FDA-approved for use in cosmetics and it is used in some tattoo inks. It can also be used as a phosphate remover from home aquaria
2.
Chemistry
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Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter. Chemistry is sometimes called the science because it bridges other natural sciences, including physics. For the differences between chemistry and physics see comparison of chemistry and physics, the history of chemistry can be traced to alchemy, which had been practiced for several millennia in various parts of the world. The word chemistry comes from alchemy, which referred to a set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism. An alchemist was called a chemist in popular speech, and later the suffix -ry was added to this to describe the art of the chemist as chemistry, the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία and this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, which is in turn derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian. Alternately, al-kīmīā may derive from χημεία, meaning cast together, in retrospect, the definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. The term chymistry, in the view of noted scientist Robert Boyle in 1661, in 1837, Jean-Baptiste Dumas considered the word chemistry to refer to the science concerned with the laws and effects of molecular forces. More recently, in 1998, Professor Raymond Chang broadened the definition of chemistry to mean the study of matter, early civilizations, such as the Egyptians Babylonians, Indians amassed practical knowledge concerning the arts of metallurgy, pottery and dyes, but didnt develop a systematic theory. Greek atomism dates back to 440 BC, arising in works by such as Democritus and Epicurus. In 50 BC, the Roman philosopher Lucretius expanded upon the theory in his book De rerum natura, unlike modern concepts of science, Greek atomism was purely philosophical in nature, with little concern for empirical observations and no concern for chemical experiments. Work, particularly the development of distillation, continued in the early Byzantine period with the most famous practitioner being the 4th century Greek-Egyptian Zosimos of Panopolis. He formulated Boyles law, rejected the four elements and proposed a mechanistic alternative of atoms. Before his work, though, many important discoveries had been made, the Scottish chemist Joseph Black and the Dutchman J. B. English scientist John Dalton proposed the theory of atoms, that all substances are composed of indivisible atoms of matter. Davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current, british William Prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. The inert gases, later called the noble gases were discovered by William Ramsay in collaboration with Lord Rayleigh at the end of the century, thereby filling in the basic structure of the table. Organic chemistry was developed by Justus von Liebig and others, following Friedrich Wöhlers synthesis of urea which proved that organisms were, in theory
3.
Iron
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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
4.
Oxidation state
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The oxidation state, often called the oxidation number, is an indicator of the degree of oxidation of an atom in a chemical compound. This is never exactly true for real bonds, the term oxidation was first used by Lavoisier to signify reaction of a substance with oxygen. Much later, it was realized that the substance, upon being oxidized, loses electrons, oxidation states are typically represented by integers. In some cases, the oxidation state of an element is a fraction. It is predicted that even a +10 oxidation state may be achieveable by platinum in the platinum tetroxide dication, the increase in oxidation state of an atom, through a chemical reaction, is known as an oxidation, a decrease in oxidation state is known as a reduction. Such reactions involve the transfer of electrons, a net gain in electrons being a reduction. For pure elements, the state is zero. There are various methods for determining oxidation states, in inorganic nomenclature, the oxidation state is determined and expressed as an oxidation number, and is represented by a Roman numeral placed after the element name. In coordination chemistry, oxidation number is defined differently from oxidation state, a “Comprehensive definition of oxidation state ” has been published with free access. This article is a distillation of an IUPAC technical report Toward a comprehensive definition of oxidation state. Exceptions to this are that hydrogen has a state of −1 in hydrides of active metals, e. g. LiH. There are two different methods for determining the state of elements in chemical compounds. First a method based on the rules in the IUPAC definition, second, a method based on the relative electronegativity of the elements in the compound, where the more electronegative element is assumed to take the negative charge. Any pure element—even if it forms diatomic molecules like chlorine —has an oxidation state of zero, examples of this are Cu or O2. For monatomic ions, the state is the same as the charge of the ion. For example, the anion has an oxidation state of −2. The sum of oxidation states for all atoms in a molecule or polyatomic ion is equal to the charge of the molecule or ion, thus, the oxidation state of one element can be calculated from the oxidation states of the other elements. An application of this rule is that the sum of the states of all atoms in a neutral molecule must be zero
5.
Ferric
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Ferric refers to iron-containing materials or compounds. In chemistry the term is reserved for iron with an number of +3. On the other hand, ferrous refers to iron with oxidation number of +2, iron is usually the most stable form of iron in air, as illustrated by the pervasiveness of rust, an insoluble iron-containing material. The word ferric is derived from the Latin word ferrum for iron, examples include iron-sulfur clusters, oxyhemoglobin, ferritin, and the cytochromes. The bioavailability of iron is of great interest because all forms of life require iron. Iron-deficiency anemia illustrates the problems resulting from low iron intake, many foods contain soluble iron compounds and are therefore necessary for good nutrition. The low bioavailability of iron affects all forms of life, bacteria secrete iron-attracting agents called siderophores that form soluble compounds of iron that can be reabsorbed into the cell and used in building iron-containing metalloproteins. The impact of increasing the bioavailability of iron was famously demonstrated by an experiment where an area of the ocean surface was sprayed with iron salts. After several days, the phytoplankton within the treated area bloomed to such an extent that the effect was visible from outer space and this fertilizing process has been proposed as a means to mitigate the carbon dioxide content of the atmosphere. Ferric iron mitigates the eutrophication of lakes by reducing the bioavailability of phosphorus in the water, mitigation arises because ferric phosphate is insoluble. Like iron, phosphate is often a limiting nutrient, and its reduction in concentration from solution limits the growth of algae, in water, ferric iron forms compounds that are often insoluble, at least near neutral pH. A salt of ferric iron hydrolyzes water and produces iron oxide-hydroxides while contributing hydrogen ions to the solution, in contrast, typical Na+ salts dissolve in water without lowering the pH. Aluminium behaves similarly to ferric ion, rust, a mixture of ferric hydroxide compounds, illustrates the low solubility of ferric ions in water. Various reagents cause rust to dissolve even at neutral pH and these ligands include EDTA, which forms a chelate complex with the ion, displacing the hydroxide and oxide ligands that comprise rust. For this reason, EDTA is often used to iron deposits or to deliver soluble iron in fertilizers. Citrate also solubilizes ferric ion at neutral pH, although its complexes are less stable than those of EDTA, Ferric iron is a d5 center, meaning that the metal has five valence electrons in the 3d orbital shell. The magnetism of ferric compounds is determined by these five electrons. Usually ferric ions are surrounded by six ligands arranged in octahedron, sometimes three and sometimes as many as seven ligands are observed
6.
Trivalent
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In chemistry, the valence or valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules. The concept of valence was developed in the half of the 19th century and was successful in explaining the molecular structure of inorganic and organic compounds. The combining power or affinity of an atom of an element was determined by the number of atoms that it combined with. In methane, carbon has a valence of 4, in ammonia, nitrogen has a valence of 3, in water, oxygen has a valence of 2, and in hydrogen chloride, chlorine has a valence of 1. Chlorine, as it has a valence of one, can be substituted for hydrogen, so phosphorus has a valence of 5 in phosphorus pentachloride, PCl5. Valence diagrams of a compound represent the connectivity of the elements, examples are, Valence only describes connectivity, it does not describe the geometry of molecular compounds, or what are now known to be ionic compounds or giant covalent structures. A line between atoms does not represent a pair of electrons as it does in Lewis diagrams and this definition differs from the IUPAC definition as an element can be said to have more than one valence. It is in manner, according to Frankland, that their affinities are best satisfied. Following these examples and postulates, Frankland declares how obvious it is that This “combining power” was afterwards called quantivalence or valency. In 1857 August Kekulé proposed fixed valences for many elements, such as 4 for carbon, and used them to propose structural formulas for many organic molecules, which are still accepted today. Most 19th-century chemists defined the valence of an element as the number of its bonds without distinguishing different types of valence or of bond. For main-group elements, in 1904 Richard Abegg considered positive and negative valences, in 1916, Gilbert N. Lewis explained valence and chemical bonding in terms of a tendency of atoms to achieve a stable octet of 8 valence-shell electrons. According to Lewis, covalent bonding leads to octets by the sharing of electrons, the term covalence is attributed to Irving Langmuir, who stated in 1919 that the number of pairs of electrons which any given atom shares with the adjacent atoms is called the covalence of that atom. The prefix co- means together, so that a co-valent bond means that the share a valence. Pauling also considered hypervalent molecules, in which main-group elements have apparent valences greater than the maximal of 4 allowed by the octet rule. Similar calculations on transition-metal molecules show that the role of p orbitals is minor, so that one s, for elements in the main groups of the periodic table, the valence can vary between 1 and 7. Many elements have a common valence related to their position in the periodic table, the Latin/Greek prefixes uni-/mono-, bi-/di-, ter-/tri-, quadri-/tetra- and quinque-/penta- are used to describe ions in the charge states 1,2,3,4,5 respectively. Polyvalence or multivalence refers to species that are not restricted to a number of valence bonds
7.
IUPAC
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The International Union of Pure and Applied Chemistry /ˈaɪjuːpæk/ or /ˈjuːpæk/ is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Council for Science, IUPAC is registered in Zürich, Switzerland, and the administrative office, known as the IUPAC Secretariat, is in Research Triangle Park, North Carolina, United States. This administrative office is headed by IUPACs executive director, currently Lynn Soby, IUPAC was established in 1919 as the successor of the International Congress of Applied Chemistry for the advancement of chemistry. Its members, the National Adhering Organizations, can be national chemistry societies, national academies of sciences, there are fifty-four National Adhering Organizations and three Associate National Adhering Organizations. IUPACs Inter-divisional Committee on Nomenclature and Symbols is the world authority in developing standards for the naming of the chemical elements. Since its creation, IUPAC has been run by different committees with different responsibilities. These committees run different projects which include standardizing nomenclature, finding ways to bring chemistry to the world, IUPAC is best known for its works standardizing nomenclature in chemistry and other fields of science, but IUPAC has publications in many fields including chemistry, biology and physics. IUPAC is also known for standardizing the atomic weights of the elements through one of its oldest standing committees, the need for an international standard for chemistry was first addressed in 1860 by a committee headed by German scientist Friedrich August Kekulé von Stradonitz. This committee was the first international conference to create an international naming system for organic compounds, the ideas that were formulated in that conference evolved into the official IUPAC nomenclature of organic chemistry. IUPAC stands as a legacy of this meeting, making it one of the most important historical international collaborations of chemistry societies, since this time, IUPAC has been the official organization held with the responsibility of updating and maintaining official organic nomenclature. IUPAC as such was established in 1919, one notable country excluded from this early IUPAC is Germany. Germanys exclusion was a result of prejudice towards Germans by the Allied powers after World War I, Germany was finally admitted into IUPAC during 1929. However, Nazi Germany was removed from IUPAC during World War II, during World War II, IUPAC was affiliated with the Allied powers, but had little involvement during the war effort itself. After the war, East and West Germany were eventually readmitted to IUPAC, since World War II, IUPAC has been focused on standardizing nomenclature and methods in science without interruption. In 2016, IUPAC denounced the use of chlorine as a chemical weapon, the letter stated, Our organizations deplore the use of chlorine in this manner. According to the CWC, the use, stockpiling, distribution, IUPAC is governed by several committees that all have different responsibilities. Each committee is made up of members of different National Adhering Organizations from different countries, the steering committee hierarchy for IUPAC is as follows, All committees have an allotted budget to which they must adhere. Any committee may start a project, if a projects spending becomes too much for a committee to continue funding, it must take the issue to the Project Committee
8.
Iron(III) oxide
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Iron oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the two being iron oxide, which is rare, and iron oxide, which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the source of iron for the steel industry. Fe2O3 is ferromagnetic, dark red, and readily attacked by acids, Iron oxide is often called rust, and to some extent this label is useful, because rust shares several properties and has a similar composition. To a chemist, rust is considered a material, described as hydrated ferric oxide. Fe2O3 can be obtained in various polymorphs, in the main ones, α and γ, iron adopts octahedral coordination geometry. That is, each Fe center is bound to six oxygen ligands, α-Fe2O3 has the rhombohedral, corundum structure and is the most common form. It occurs naturally as the mineral hematite which is mined as the ore of iron. It is antiferromagnetic below ~260 K, and exhibits weak ferromagnetism between 260 K and the Néel temperature,950 K and it is easy to prepare using both thermal decomposition and precipitation in the liquid phase. Its magnetic properties are dependent on many factors, e. g. pressure, particle size and it is metastable and converted from the alpha phase at high temperatures. It occurs naturally as the mineral maghemite and it is ferromagnetic and finds application in recording tapes, although ultrafine particles smaller than 10 nanometers are superparamagnetic. It can be prepared by thermal dehydratation of gamma iron oxide-hydroxide, another method involves the careful oxidation of Fe3O4. The ultrafine particles can be prepared by decomposition of iron oxalate. Several other phases have been identified or claimed, the β-phase is cubic body centered, metastable, and at temperatures above 500 °C converts to alpha phase. It can be prepared by reduction of hematite by carbon, pyrolysis of iron chloride solution, the epsilon phase is rhombic, and shows properties intermediate between alpha and gamma, and may have useful magnetic properties. Preparation of the pure epsilon phase has proven challenging due to contamination with alpha. Material with a proportion of epsilon phase can be prepared by thermal transformation of the gamma phase. This phase is metastable, transforming to the alpha phase at between 500 and 750 °C
9.
Pourbaix diagram
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In chemistry, a Pourbaix diagram, also known as a potential/pH diagram, EH-pH diagram or a pE/pH diagram, maps out possible stable phases of an aqueous electrochemical system. Predominant ion boundaries are represented by lines, as such a Pourbaix diagram can be read much like a standard phase diagram with a different set of axes. Similarly to phase diagrams, they do not allow for reaction rate or kinetic effects, the diagrams are named after Marcel Pourbaix, the Russian-born, Belgian chemist who invented them. Pourbaix diagrams are also known as EH-pH diagrams due to the labeling of the two axes, the vertical axis is labeled EH for the voltage potential with respect to the standard hydrogen electrode as calculated by the Nernst equation. The H stands for hydrogen, although other standards may be used, E H = E0 −0.0592 n log c d a b The horizontal axis is labeled pH for the -log function of the H+ ion activity. PH = − log 10 = log 10 The lines in the Pourbaix diagram show the conditions, that is. On either side of the line, one form of the species will instead be said to be predominant, in order to draw the position of the lines with the Nernst equation, the activity of the chemical species at equilibrium must be defined. Usually, the activity of a species is approximated as equal to the concentration or partial pressure, the same values should be used for all species present in the system. For soluble species, the lines are drawn for concentrations of 1 M or 10−6 M. Sometimes additional lines are drawn for other concentrations, while such diagrams can be drawn for any chemical system, it is important to note that the addition of a metal binding agent will often modify the diagram. For instance, carbonate has an effect upon the diagram for uranium. The presence of trace amounts of species such as chloride ions can also greatly affect the stability of certain species by destroying passivating layers. In addition, changes in temperature and concentration of solvated ions in solution will shift the lines in accordance with the Nernst equation. The diagrams also do not take kinetic effects into account, meaning that species shown as unstable might not react to any significant degree in practice, a simplified Pourbaix diagram indicates regions of Immunity, Corrosion and Passivity, instead of the stable species. They thus give a guide to the stability of a metal in a specific environment. Immunity means that the metal is not attacked, while corrosion shows that general attack will occur, the equation must be balanced for M, H, O and charge. A standard Gibbs free energy ΔGo is associated with each equation, a base-balanced equation can be converted to an acid-balanced equation using the equlibrium constant for the self-ionization of water, and only acid-balanced equations are considered below. In the following, the Nernst slope ∆=RT/F is used, which has a value of 0.02569, when base-10 logarithms are used, ∆λ =0.05916
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