Editing Molecule (section)

{{Short description| Electrically neutral group of two or more atoms}}
{{Other uses}}
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{{more footnotes needed|date=March 2023}}
{{Use dmy dates|date=February 2016}}
[[File:PTCDA AFM.jpg|thumb|[[Atomic force microscopy]] (AFM) image of a [[Perylenetetracarboxylic dianhydride|PTCDA]] molecule, in which the five six-carbon rings are visible.<ref>{{cite journal|doi=10.1038/ncomms8766|pmid=26178193|pmc=4518281|title=Chemical structure imaging of a single molecule by atomic force microscopy at room temperature|journal=Nature Communications|volume=6|page=7766|year=2015|last1=Iwata|first1=Kota|last2=Yamazaki|first2=Shiro|last3=Mutombo|first3=Pingo|last4=Hapala|first4=Prokop|last5=Ondráček|first5=Martin|last6=Jelínek|first6=Pavel|last7=Sugimoto|first7=Yoshiaki|bibcode= 2015NatCo...6.7766I}}</ref>]]
[[File:Pentacene on Ni(111) STM.jpg|thumb|A [[scanning tunneling microscopy]] image of [[pentacene]] molecules, which consist of linear chains of five carbon rings.<ref>{{cite journal|doi=10.1039/C4NR07057G|pmid=25619890|title=Pentacene on Ni(111): Room-temperature molecular packing and temperature-activated conversion to graphene|journal=Nanoscale|volume=7|issue=7|pages=3263–9|year=2015|last1=Dinca|first1=L.E.|last2=De Marchi|first2=F.|last3=MacLeod|first3=J.M.|last4=Lipton-Duffin|first4=J.|last5=Gatti|first5=R.|last6=Ma|first6=D.|last7=Perepichka|first7=D.F.|last8=Rosei|first8=F.|author-link7=Dmitrii Perepichka|bibcode= 2015Nanos...7.3263D}}</ref>]]
[[File:TOAT AFM.png|thumb|AFM image of 1,5,9-trioxo-13-azatriangulene and its chemical structure.<ref>{{cite journal|doi=10.1038/ncomms11560|pmid=27230940|pmc=4894979|title=Mapping the electrostatic force field of single molecules from high-resolution scanning probe images|journal=Nature Communications|volume=7|pages=11560|year=2016|last1=Hapala|first1=Prokop|last2=Švec|first2=Martin|last3=Stetsovych|first3=Oleksandr|last4=Van Der Heijden|first4=Nadine J.|last5=Ondráček|first5=Martin|last6=Van Der Lit|first6=Joost|last7=Mutombo|first7=Pingo|last8=Swart|first8=Ingmar|last9=Jelínek|first9=Pavel|bibcode=2016NatCo...711560H}}</ref>]]

A '''molecule''' is a group of two or more [[atom]]s that are held together by [[Force|attractive forces]] known as [[chemical bond]]s; depending on context, the term may or may not include [[ions]] that satisfy this criterion.<ref name="iupac">{{GoldBookRef| title=Molecule|file=M04002|accessdate=23 February 2016}}</ref><ref>{{cite book| author= Ebbin, Darrell D.| title= General Chemistry |edition=3rd| date= 1990| publisher= [[Houghton Mifflin Co.]]| location= Boston| isbn= 978-0-395-43302-7}}</ref><ref>{{cite book| author= Brown, T.L. |author2=Kenneth C. Kemp |author3=Theodore L. Brown |author4=Harold Eugene LeMay |author5=Bruce Edward Bursten |title= Chemistry – the Central Science | url= https://archive.org/details/studentlectureno00theo | url-access= registration |edition=9th| date= 2003| publisher= [[Prentice Hall]]| location= New Jersey| isbn= 978-0-13-066997-1}}</ref><ref>{{cite book| last= Chang| first= Raymond| title= Chemistry | url= https://archive.org/details/chemistry00chan_0| url-access= registration|edition=6th| date= 1998| publisher= [[McGraw Hill]]| location= New York| isbn= 978-0-07-115221-1}}</ref><ref>{{cite book| author= Zumdahl, Steven S.| title= Chemistry |edition=4th| date= 1997| publisher= Houghton Mifflin| location= Boston| isbn= 978-0-669-41794-4}}</ref> In [[quantum physics]], [[organic chemistry]], and [[biochemistry]], the distinction from ions is dropped and ''molecule'' is often used when referring to [[polyatomic ion]]s.

A molecule may be [[homonuclear]], that is, it consists of atoms of one [[chemical element]], e.g. two atoms in the [[oxygen]] molecule (O<sub>2</sub>); or it may be [[heteronuclear]], a [[chemical compound]] composed of more than one element, e.g. [[water (molecule)|water]] (two hydrogen atoms and one oxygen atom; H<sub>2</sub>O). In the [[kinetic theory of gases]], the term ''molecule'' is often used for any gaseous [[particle]] regardless of its composition. This relaxes the requirement that a molecule contains two or more atoms, since the [[noble gases]] are individual atoms.<ref>{{cite book |last=Chandra |first=Sulekh |title=Comprehensive Inorganic Chemistry |date=2005 |publisher=New Age Publishers |isbn=978-81-224-1512-4}}</ref> Atoms and complexes connected by [[non-covalent interactions]], such as [[hydrogen bond]]s or [[ionic bond]]s, are typically not considered single molecules.<ref>{{cite encyclopedia|title=Molecule|encyclopedia=[[Encyclopædia Britannica]]|date=22 January 2016|url=http://global.britannica.com/science/molecule|access-date=23 February 2016|archive-date=3 May 2020|archive-url=https://web.archive.org/web/20200503044729/https://global.britannica.com/science/molecule|url-status=live}}</ref>

Concepts similar to molecules have been discussed since ancient times, but modern investigation into the nature of molecules and their bonds began in the 17th century. Refined over time by scientists such as [[Robert Boyle]], [[Amedeo Avogadro]], [[Jean Baptiste Perrin|Jean Perrin]], and [[Linus Pauling]], the study of molecules is today known as [[molecular physics]] or molecular chemistry.