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Portal:Chemistry

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Introduction

Chemistry is the scientific discipline involved with compounds composed of atoms, i.e. elements, and molecules, i.e. combinations of atoms: their composition, structure, properties, behavior and the changes they undergo during a reaction with other compounds. Chemistry addresses topics such as how atoms and molecules interact via chemical bonds to form new chemical compounds. There are four types of chemical bonds: covalent bonds, in which compounds share one or more electron(s); ionic bonds, in which a compound donates one or more electrons to another compound to produce ions (cations and anions); hydrogen bonds; and Van der Waals force bonds.

In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. Examples include plant chemistry (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties of the soil on the moon (astrophysics), how medications work (pharmacology), and how to collect DNA evidence at a crime scene (forensics).

The history of chemistry spans a period from very old times to the present. Since several millennia BC, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. Examples include extracting metals from ores, making pottery and glazes, fermenting beer and wine, extracting chemicals from plants for medicine and perfume, rendering fat into soap, making glass, and making alloys like bronze. Chemistry was preceded by its protoscience, alchemy, which is an intuitive but non-scientific approach to understanding the constituents of matter and their interactions. It was unsuccessful in explaining the nature of matter and its transformations, but, by performing experiments and recording the results, alchemists set the stage for modern chemistry. Chemistry as a body of knowledge distinct from alchemy began to emerge when a clear differentiation was made between them by Robert Boyle in his work The Sceptical Chymist (1661). While both alchemy and chemistry are concerned with matter and its transformations, the crucial difference was given by the scientific method that chemists employed in their work. Chemistry is considered to have become an established science with the work of Antoine Lavoisier, who developed a law of conservation of mass that demanded careful measurement and quantitative observations of chemical phenomena. The history of chemistry is intertwined with the history of thermodynamics, especially through the work of Willard Gibbs.

Featured article

Technetium.svg
Technetium is a chemical element that has the symbol Tc and the atomic number 43. Pronounced tek-nee-s(h)ee-um, the chemical properties of this silvery grey, radioactive, crystalline transition metal are intermediate between rhenium and manganese. Its short-lived isotope Tc-99m is used in nuclear medicine for a wide variety of diagnostic tests. Tc-99 is used as a gamma ray-free source of beta particles, and its pertechnetate ion (TcO
4
) could find use as an anodic corrosion preventer for steel (this possible use is hindered by technetium's radioactivity). The pertechnetate forms a technetium dioxide layer on the steel surface, this TcO2 formation explains how iron powder can be used to remove technetium from water. It is also possible to absorb technetium on activated carbon.

Dmitri Mendeleev predicted many of the properties of element 43, which he called ekamanganese, well before its actual discovery (see Mendeleev's predicted elements). In 1937 its isotope Tc-97 became the first element to be artificially produced, hence its name (from the Greek τεχνητος, meaning "artificial"). Most technetium produced on Earth is a by-product of fission of uranium-235 in nuclear reactors and is extracted from nuclear fuel rods. No isotope of technetium has a half-life longer than 4.2 million years (Tc-98), so its detection in red giants in 1952 helped bolster the theory that stars can produce heavier elements. On earth, technetium occurs naturally only in uranium ores as a product of spontaneous fission; the quantities are minute but have been measured.

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Categories

History and Philosophy of Chemistry

Antoine Lavoisier

Many chemists have an interest in the history of chemistry. Those with philosophical interests will be interested that the philosophy of chemistry has quite recently developed along a path somewhat different from the general philosophy of science.

Other articles that might interest you are:

There is a Wikipedia Project on the History of Science and a portal for the philosophy of science.

Chemistry Resources

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Wikipedia:WikiProject Chemicals/Data is a collection of links and references that are useful for chemistry-related works. This includes free online chemical databases, publications, patents, computer programs, and various tools.

Science is Fun University of Wisconsin–Madison Chemistry Professor Bassam Z. Shakhashiri, shares the fun of science.

unit-conversion.info A good place to figure out what equals what.

General Chemistry Online Clear text and comprehensive coverage of general chemistry topics by Fred Senese, Dept. of Chemistry Frostburg State University

General Chemistry Demonstration at Purdue Video clips (and descriptions) of lecture demonstrations.

Intota Chemistry Experts A large online listing of real-world chemistry expert biographies provides examples of the many areas of expertise and careers in chemistry.

Chemistry Webercises Directory A large listing of chemistry resources maintained by Steven Murov, Emeritus Chemistry Professor Modesto Junior College.

MathMol MathMol (Mathematics and Molecules) is a good starting point for those interested in the field of molecular modeling.

Chemistry Educational Resources and Essential References from Wiley, the world's largest chemistry publisher

ABC-Chemistry A directory of free full-text journals in chemistry, biochemistry and related subjects.

The Element Song A goofy little song about all of the elements.

Selected biography

Louis Pasteur
Louis Pasteur (1822-1895) was a French microbiologist and chemist. He was the first to demonstrate chirality of molecules, using tartaric acid crystals, but this achievement is often overlooked in favor of his more famous work in biology and medicine. He is best known for demonstrating how to prevent milk and wine from going sour, a process which came to be called pasteurization. His experiments confirmed the germ theory of disease, and he created the first vaccine for rabies. He became one of the main founders of bacteriology, the other major figure being Robert Koch. Pasteur also discovered anaerobiosis, whereby some microorganisms can develop and live without air or oxygen.

Techniques used by chemists

Equipment used by chemists

Chemistry in society

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Periodic Table

Group 1 2 3   4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Alkali metals Alkaline earth metals Pnicto­gens Chal­co­gens Halo­gens Noble gases
Period

1

Hydro­gen1H1.008 He­lium2He4.0026
2 Lith­ium3Li6.94 Beryl­lium4Be9.0122 Boron5B10.81 Carbon6C12.011 Nitro­gen7N14.007 Oxy­gen8O15.999 Fluor­ine9F18.998 Neon10Ne20.180
3 So­dium11Na22.990 Magne­sium12Mg24.305 Alumin­ium13Al26.982 Sili­con14Si28.085 Phos­phorus15P30.974 Sulfur16S32.06 Chlor­ine17Cl35.45 Argon18Ar39.948
4 Potas­sium19K39.098 Cal­cium20Ca40.078 Scan­dium21Sc44.956 Tita­nium22Ti47.867 Vana­dium23V50.942 Chrom­ium24Cr51.996 Manga­nese25Mn54.938 Iron26Fe55.845 Cobalt27Co58.933 Nickel28Ni58.693 Copper29Cu63.546 Zinc30Zn65.38 Gallium31Ga69.723 Germa­nium32Ge72.630 Arsenic33As74.922 Sele­nium34Se78.971 Bromine35Br79.904 Kryp­ton36Kr83.798
5 Rubid­ium37Rb85.468 Stront­ium38Sr87.62 Yttrium39Y88.906 Zirco­nium40Zr91.224 Nio­bium41Nb92.906 Molyb­denum42Mo95.95 Tech­netium43Tc​[98] Ruthe­nium44Ru101.07 Rho­dium45Rh102.91 Pallad­ium46Pd106.42 Silver47Ag107.87 Cad­mium48Cd112.41 Indium49In114.82 Tin50Sn118.71 Anti­mony51Sb121.76 Tellur­ium52Te127.60 Iodine53I126.90 Xenon54Xe131.29
6 Cae­sium55Cs132.91 Ba­rium56Ba137.33 Lan­thanum57La138.91 1 asterisk Haf­nium72Hf178.49 Tanta­lum73Ta180.95 Tung­sten74W183.84 Rhe­nium75Re186.21 Os­mium76Os190.23 Iridium77Ir192.22 Plat­inum78Pt195.08 Gold79Au196.97 Mer­cury80Hg200.59 Thallium81Tl204.38 Lead82Pb207.2 Bis­muth83Bi208.98 Polo­nium84Po​[209] Asta­tine85At​[210] Radon86Rn​[222]
7 Fran­cium87Fr​[223] Ra­dium88Ra​[226] Actin­ium89Ac​[227] 1 asterisk Ruther­fordium104Rf​[267] Dub­nium105Db​[268] Sea­borgium106Sg​[269] Bohr­ium107Bh​[270] Has­sium108Hs​[270] Meit­nerium109Mt​[278] Darm­stadtium110Ds​[281] Roent­genium111Rg​[282] Coper­nicium112Cn​[285] Nihon­ium113Nh​[286] Flerov­ium114Fl​[289] Moscov­ium115Mc​[290] Liver­morium116Lv​[293] Tenness­ine117Ts​[294] Oga­nesson118Og​[294]
1 asterisk Cerium58Ce140.12 Praseo­dymium59Pr140.91 Neo­dymium60Nd144.24 Prome­thium61Pm​[145] Sama­rium62Sm150.36 Europ­ium63Eu151.96 Gadolin­ium64Gd157.25 Ter­bium65Tb158.93 Dyspro­sium66Dy162.50 Hol­mium67Ho164.93 Erbium68Er167.26 Thulium69Tm168.93 Ytter­bium70Yb173.05 Lute­tium71Lu174.97  
1 asterisk Thor­ium90Th232.04 Protac­tinium91Pa231.04 Ura­nium92U238.03 Neptu­nium93Np​[237] Pluto­nium94Pu​[244] Ameri­cium95Am​[243] Curium96Cm​[247] Berkel­ium97Bk​[247] Califor­nium98Cf​[251] Einstei­nium99Es​[252] Fer­mium100Fm​[257] Mende­levium101Md​[258] Nobel­ium102No​[259] Lawren­cium103Lr​[266]

Note: Nihonium, moscovium, tennessine, and oganesson have only recently been named.

Things you can do

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Collaboration of the Month

Nuvola apps edu science.png The current Chemistry Article Improvement Drive is Sodium hydroxide.
Every month a different chemistry-related topic, stub or non-existent article may be picked. Please improve the article any way you can.

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  1. ^ Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305. 
  2. ^ IUPAC 2016, Table 2, 3 combined; uncertainty removed.