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by | Mar 12, 2018 | Hepatica

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Introduction

Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during reactions with other substances. Chemistry also addresses the nature of chemical bonds in chemical compounds.

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. For example, chemistry explains aspects of plant growth (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 (cosmochemistry), how medications work (pharmacology), and how to collect DNA evidence at a crime scene (forensics).

Chemistry has existed under various names since ancient times. It has evolved, and now chemistry encompasses various areas of specialisation, or subdisciplines, that continue to increase in number and interrelate to create further interdisciplinary fields of study. The applications of various fields of chemistry are used frequently for economic purposes in the chemical industry. (Full article...)

Selected article

Helium discharge tube shaped like the element's atomic symbol
Helium is a chemical element; its atomic symbol is He. It is a colorless, odorless, tasteless, non-toxic, and nearly inert monatomic that heads the noble gas series in the periodic table. Its atomic number is 2 and its boiling and melting points are the lowest among the elements. It exists only as a gas except in extreme conditions. Extreme conditions are also needed to create the small handful of helium compounds, which are all unstable at standard temperature and pressure. Its most abundant stable isotope is helium-4 and it has a rare stable isotope, helium-3. The behavior of liquid helium-4's two different states—helium I and helium II—is important to researchers studying quantum mechanics (in particular the phenomenon of superfluidity) and those looking at the effects that near absolute zero temperatures have on matter (such as superconductivity).

Helium is the second most abundant element in the known Universe and second lightest element in the periodic table. In the modern Universe almost all new helium is created as a result of the nuclear fusion of hydrogen in stars. On Earth it is created by the radioactive decay of much heavier elements (alpha particles are helium-4 nuclei produced by alpha-decay). After its creation, part of it is trapped with natural gas in concentrations up to 7% by volume. It is extracted from the natural gas by a low temperature separation process called fractional distillation.

In 1868 the French astronomer Pierre Janssen first detected helium as an unknown yellow spectral line signature in light from a solar eclipse. (The word helium comes from ancient Greek ἥλιος which is, surprisingly, cognate with the English sun.) Since then large reserves of helium have been found in the natural gas fields of the United States, which is by far the largest supplier of the gas. Helium is used in cryogenics, in deep-sea breathing systems, to cool superconducting magnets, in helium dating, for inflating balloons, for providing lift in airships and as a protective gas for many industrial uses (such as arc welding and growing silicon wafers). Inhaling a small volume of the gas temporarily changes the quality of one's voice.

Subcategories

History and Philosophy of Chemistry

Antoine Lavoisier
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.

Chemistry Resources

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.

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.

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.

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.

Show chemistry resources...

Selected image

Malachite
Malachite
Malachite is a carbonate mineral, copper(II) carbonate hydroxide Cu2CO3(OH)2. It crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses. Its beauty may be seen most strikingly in the Malachite Room at the Hermitage in Saint Petersburg.

Selected biography

Harold Urey
Harold Urey (1893-1981) was an American physical chemist, who won the 1934 Nobel Prize in Chemistry for his work on isotopes, specifically the discovery of deuterium, a hydrogen isotope, and the production of heavy water. He also performed pioneering research in cosmochemistry, which studies the origin and development of elements and their isotopes, primarily within the solar system. Urey, along with his student Stanley Miller, may be best remembered for the renowned Miller-Urey experiment, which shows that a mixture of ammonia, methane and hydrogen, when exposed to ultraviolet radiation and water, can interact to form amino acids, the "building blocks" of terrestrial life. This experiment followed on from Urey's work on the oxygen isotope 18O, and is considered to be pioneering work in the field of paleoclimatology, as it attempts to explain the composition of the early Earth's atmosphere.

Techniques used by chemists

Equipment used by chemists

Chemistry in society

Chemistry in industry

WikiProjects

Topics

Periodic Table

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

1

Hydro­gen1H​1.0080 He­lium2He​4.0026
2 Lith­ium3Li​6.94 Beryl­lium4Be​9.0122 Boron5B​10.81 Carbon6C​12.011 Nitro­gen7N​14.007 Oxy­gen8O​15.999 Fluor­ine9F​18.998 Neon10Ne​20.180
3 So­dium11Na​22.990 Magne­sium12Mg​24.305 Alumin­ium13Al​26.982 Sili­con14Si​28.085 Phos­phorus15P​30.974 Sulfur16S​32.06 Chlor­ine17Cl​35.45 Argon18Ar​39.95
4 Potas­sium19K​39.098 Cal­cium20Ca​40.078 Scan­dium21Sc​44.956 Tita­nium22Ti​47.867 Vana­dium23V​50.942 Chrom­ium24Cr​51.996 Manga­nese25Mn​54.938 Iron26Fe​55.845 Cobalt27Co​58.933 Nickel28Ni​58.693 Copper29Cu​63.546 Zinc30Zn​65.38 Gallium31Ga​69.723 Germa­nium32Ge​72.630 Arsenic33As​74.922 Sele­nium34Se​78.971 Bromine35Br​79.904 Kryp­ton36Kr​83.798
5 Rubid­ium37Rb​85.468 Stront­ium38Sr​87.62 Yttrium39Y​88.906 Zirco­nium40Zr​91.224 Nio­bium41Nb​92.906 Molyb­denum42Mo​95.95 Tech­netium43Tc​[97] Ruthe­nium44Ru​101.07 Rho­dium45Rh​102.91 Pallad­ium46Pd​106.42 Silver47Ag​107.87 Cad­mium48Cd​112.41 Indium49In​114.82 Tin50Sn​118.71 Anti­mony51Sb​121.76 Tellur­ium52Te​127.60 Iodine53I​126.90 Xenon54Xe​131.29
6 Cae­sium55Cs​132.91 Ba­rium56Ba​137.33 1 asterisk Lute­tium71Lu​174.97 Haf­nium72Hf​178.49 Tanta­lum73Ta​180.95 Tung­sten74W​183.84 Rhe­nium75Re​186.21 Os­mium76Os​190.23 Iridium77Ir​192.22 Plat­inum78Pt​195.08 Gold79Au​196.97 Mer­cury80Hg​200.59 Thallium81Tl​204.38 Lead82Pb​207.2 Bis­muth83Bi​208.98 Polo­nium84Po​[209] Asta­tine85At​[210] Radon86Rn​[222]
7 Fran­cium87Fr​[223] Ra­dium88Ra​[226] 1 asterisk Lawren­cium103Lr​[266] Ruther­fordium104Rf​[267] Dub­nium105Db​[268] Sea­borgium106Sg​[269] Bohr­ium107Bh​[270] Has­sium108Hs​[269] Meit­nerium109Mt​[278] Darm­stadtium110Ds​[281] Roent­genium111Rg​[282] Coper­nicium112Cn​[285] Nihon­ium113Nh​[286] Flerov­ium114Fl​[289] Moscov­ium115Mc​[290] Liver­morium116Lv​[293] Tenness­ine117Ts​[294] Oga­nesson118Og​[294]
1 asterisk Lan­thanum57La​138.91 Cerium58Ce​140.12 Praseo­dymium59Pr​140.91 Neo­dymium60Nd​144.24 Prome­thium61Pm​[145] Sama­rium62Sm​150.36 Europ­ium63Eu​151.96 Gadolin­ium64Gd​157.25 Ter­bium65Tb​158.93 Dyspro­sium66Dy​162.50 Hol­mium67Ho​164.93 Erbium68Er​167.26 Thulium69Tm​168.93 Ytter­bium70Yb​173.05  
1 asterisk Actin­ium89Ac​[227] Thor­ium90Th​232.04 Protac­tinium91Pa​231.04 Ura­nium92U​238.03 Neptu­nium93Np​[237] Pluto­nium94Pu​[244] Ameri­cium95Am​[243] Curium96Cm​[247] Berkel­ium97Bk​[247] Califor­nium98Cf​[251] Einstei­nium99Es​[252] Fer­mium100Fm​[257] Mende­levium101Md​[258] Nobel­ium102No​[259]

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Sources

  1. ^ Meija, Juris; 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. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
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