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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

Space-filling image of an alanine cyclol "fabric", proposed by Winrich in 1936.
The cyclol hypothesis was the first structural model of a folded, globular protein. It was developed by Dorothy Wrinch in the late 1930's, and was based on three assumptions. Firstly, the hypothesis assumes that two peptide groups can be crosslinked by a cyclol reaction; these crosslinks are covalent analogs of non-covalent hydrogen bonds between peptide groups. These reactions have been observed in the ergopeptides and other compounds. Secondly, it assumes that, under some conditions, amino acids will naturally make the maximum possible number of cyclol crosslinks, resulting in cyclol molecules and cyclol fabrics. Finally, the hypothesis assumes that globular proteins have a tertiary structure corresponding to Platonic solids and semiregular polyhedra formed of cyclol fabrics with no free edges.

Although incorrect as a model for the structure of globular proteins, several elements of the cyclol model were later verified, such as the cyclol reaction itself and the hypothesis that hydrophobic interactions are chiefly responsible for protein folding. The cyclol hypothesis stimulated many scientists to research questions in protein structure and chemistry, and was a precursor of the more accurate models hypothesized for the DNA double helix and protein secondary structure. The proposal and testing of the cyclol model also provides an excellent illustration of empirical falsifiability acting as part of the scientific method.

Selected image

Manganese(II) chloride
Credit:

Manganese(II) chloride is an ionic salt that is the only stable chloride of manganese. It occurs naturally as the mineral scacchite, and it is a weak Lewis acid.

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

Svante Arrhenius
Svante Arrhenius (1859-1927) was a Swedish chemist, and one of the founders of the science of physical chemistry. The Arrhenius equation and the lunar crater Arrhenius are named after him. Arrhenius was the first to explain the fact that neither pure salts nor pure water are conductors, but solutions of salts in water are, due to the dissociation of salt into ions. As an extension of this idea, he proposed that acids were substances which produce hydrogen ions in solution, and that bases were substances which produce hydroxide ions in solution. Arrhenius also developed a theory to explain the ice ages, and first formulated the idea that changes in the levels of carbon dioxide in the atmosphere could substantially alter the surface temperature through the greenhouse effect. He received the Nobel Prize in Chemistry in 1903.

Techniques used by chemists

Equipment used by chemists

Chemistry in society

Chemistry in industry

WikiProjects

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.
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