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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 pheesics, organic chemistry, an biochemistry, the term molecule is eften uised less strictly, an aa bein applee'd tae polyatomic ions.

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 they 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, such 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 an aa 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. An aa, 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 (such as in graphene) or three-dimensionally (such as in diamond, quartz, or sodium chloride). The theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bondin, which means that solit metals are an aa nae made o molecules. In glesses (solits that exeest in a vitreous disordered state), atoms mey an aa 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[eedit | eedit soorce]

  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.