Molecule

A molecule is an electrically neutral group o twa or mair atoms held thegither bi chemical bonds.^{[1][2][3][4][5]} Molecules are distinguished frae ions bi thair lack o electrical chairge. Houever, in quantum physics, organic chemistry, an biochemistry, the term molecule is eften uised less strictly, bein applee'd tae polyatomic ions an aa.

In the kinetic theory o gases, the term molecule is eften uised for ony gaseous pairticle regairdless o its composeetion. Accordin tae this defineetion, noble gas atoms are conseedert molecules as thay are in fact monoatomic molecules.^[6]

A molecule mey be homonuclear, that is, it conseests o atoms o ane chemical element, as wi oxygen (O₂); or it mey be heteronuclear, a chemical compoond componed o mair nor ane element, as wi watter (H₂O). Atoms an complexes connectit bi non-covalent interactions, sic as hydrogen bonds or ionic bonds, are generally nae conseedert single molecules.^[7]

Molecules as components o matter are common in organic substances (an tharefore biochemistry). Thay mak up maist o the oceans an atmosphere. Houever, the majority o fameeliar solit substances on Yird, includin maist o the minerals that mak up the crust, mantle, an core o the Yird, conteen mony chemical bonds, but are nae made o identifiable molecules. Forby, na teepical molecule can be defined for ionic creestals (sauts) an covalent creestals (network solits), awtho thir are eften componed o repeatin unit cells that extend aither in a plane (sic as in graphene) or three-dimensionally (sic as in diamond, quartz, or sodium chloride). The theme o repeated unit-cellular-structur forby holds for maist condensed phases wi metallic bondin, which means that solit metals are nae made o molecules. In glesses (solits that exeest in a vitreous disordered state), atoms mey forby be held thegither bi chemical bonds wi na presence o ony definable molecule, nor ony o the regularity o repeatin units that chairacterises creestals.

References

1. IUPAC, Compendium o Chemical Terminology, 2nt ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "Molecule".
2. Ebbin, Darrell D. (1990). General Chemistry (3rd ed.). Boston: Houghton Mifflin Co. ISBN 0-395-43302-9.
3. Brown, T.L.; Kenneth C. Kemp; Theodore L. Brown; Harold Eugene LeMay; Bruce Edward Bursten (2003). Chemistry – the Central Science (9th ed.). New Jersey: Prentice Hall. ISBN 0-13-066997-0.
4. Chang, Raymond (1998). Chemistry (6th ed.). New York: McGraw Hill. ISBN 0-07-115221-0.
5. Zumdahl, Steven S. (1997). Chemistry (4th ed.). Boston: Houghton Mifflin. ISBN 0-669-41794-7.
6. Chandra, Sulekh (2005). Comprehensive Inorganic Chemistry. New Age Publishers. ISBN 81-224-1512-1.
7. "Molecule". Encyclopædia Britannica. 22 Januar 2016. Retrieved 23 Februar 2016.