Editing Lithium (section)

=== Atomic and physical ===
[[File:Limetal.JPG|thumb|upright=0.7|left|Lithium ingots with a thin layer of black nitride tarnish]]
The [[alkali metal]]s are also called the lithium family, after its leading element. Like the other alkali metals (which are [[sodium]] (Na), [[potassium]] (K), [[rubidium]] (Rb), [[caesium]] (Cs), and [[francium]] (Fr)), lithium has a single [[valence electron]] that, in the presence of solvents, is easily released to form Li<sup>+</sup>.<ref name="krebs" /> Because of this, lithium is a good conductor of heat and electricity as well as a highly reactive element, though it is the least reactive of the alkali metals. Lithium's lower reactivity is due to the proximity of its valence electron to its [[atomic nucleus|nucleus]] (the remaining [[Two-electron atom|two electrons]] are in the [[s-orbital|1s orbital]], much lower in energy, and do not participate in chemical bonds).<ref name="krebs" /> Molten lithium is significantly more reactive than its solid form.<ref>{{Cite journal |last1=Huang |first1=Chuanfu |last2=Kresin |first2=Vitaly V. |date=June 2016 |title=Note: Contamination-free loading of lithium metal into a nozzle source |journal=Review of Scientific Instruments |language=en |volume=87 |issue=6 |page=066105 |doi=10.1063/1.4953918 |pmid=27370506 |issn=0034-6748 |bibcode=2016RScI...87f6105H}}</ref><ref>{{Cite book |title=The chemistry of the liquid alkali metals |author=Addison, C. C. |date=1984 |publisher=Wiley |isbn=978-0-471-90508-0 |location=Chichester [West Sussex] |oclc=10751785}}</ref>

Lithium metal is soft enough to be cut with a knife. It is silvery-white. In air it oxidizes to [[lithium oxide]].<ref name="krebs" /> Its [[melting point]] of {{Cvt|180.50|C|K F|disp=|abbr=unit}}<ref name="pubchemLithium">{{cite web |title=PubChem Element Summary for AtomicNumber 3, Lithium |url=https://pubchem.ncbi.nlm.nih.gov/element/Lithium |work=National Center for Biotechnology Information |date=2021 |access-date=10 September 2021 |archive-date=10 September 2021 |archive-url=https://web.archive.org/web/20210910175321/https://pubchem.ncbi.nlm.nih.gov/element/Lithium |url-status=live}}</ref> and its [[boiling point]] of {{Cvt|1342|C|K F|disp=|abbr=unit}}<ref name="pubchemLithium" /> are each the highest of all the alkali metals while its [[density]] of 0.534 [[Density#Unit|g/cm<sup>3</sup>]] is the lowest.

Lithium has a very low density (0.534&nbsp;g/cm<sup>3</sup>), comparable with [[pine wood]].<ref>{{Cite web |url=https://education.jlab.org/itselemental/ele003.html |title=It's Elemental – The Element Lithium |website=education.jlab.org |access-date=9 October 2019 |archive-date=5 October 2019 |archive-url=https://web.archive.org/web/20191005165125/https://education.jlab.org/itselemental/ele003.html |url-status=live}}</ref> It is the least dense of all elements that are solids at room temperature; the next lightest solid element (potassium, at 0.862&nbsp;g/cm<sup>3</sup>) is more than 60% denser. Apart from [[helium]] and [[hydrogen]], as a solid it is less dense than any other element as a liquid, being only two-thirds as dense as [[liquid nitrogen]] (0.808&nbsp;g/cm<sup>3</sup>).<ref>{{cite web |url=http://encyclopedia.airliquide.com/Encyclopedia.asp?LanguageID=11&CountryID=19&Formula=&GasID=5&UNNumber=&EquivGasID=32&VolLiquideBox=&MasseLiquideBox=&VolGasBox=&MasseGasBox=&RD20=29&RD9=8&RD6=64&RD4=2&RD3=22&RD8=27&RD2=20&RD18=41&RD7=18&RD13=71&RD16=35&RD12=31&RD19=34&RD24=62&RD25=77&RD26=78&RD28=81&RD29=82 |title=Nitrogen, N2, Physical properties, safety, MSDS, enthalpy, material compatibility, gas liquid equilibrium, density, viscosity, inflammability, transport properties |publisher=Encyclopedia.airliquide.com |access-date=29 September 2010 |url-status=live |archive-url=https://web.archive.org/web/20110721162642/http://encyclopedia.airliquide.com/Encyclopedia.asp?LanguageID=11&CountryID=19&Formula=&GasID=5&UNNumber=&EquivGasID=32&VolLiquideBox=&MasseLiquideBox=&VolGasBox=&MasseGasBox=&RD20=29&RD9=8&RD6=64&RD4=2&RD3=22&RD8=27&RD2=20&RD18=41&RD7=18&RD13=71&RD16=35&RD12=31&RD19=34&RD24=62&RD25=77&RD26=78&RD28=81&RD29=82 |archive-date=21 July 2011}}</ref> Lithium can float on the lightest hydrocarbon oils and is one of only three metals that can float on water, the other two being [[sodium]] and [[potassium]].
[[File:Lithium element.jpg|thumb|left|upright=0.7|Lithium floating in oil]]
Lithium's [[coefficient of thermal expansion]] is twice that of [[aluminium]] and almost four times that of [[iron]].<ref>{{cite web |url=http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html |title=Coefficients of Linear Expansion |publisher=Engineering Toolbox |archive-url=https://web.archive.org/web/20121130215248/http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html |archive-date=30 November 2012 |access-date=9 January 2011}}</ref> Lithium is [[superconductive]] below 400 [[microkelvin|μK]] at standard pressure<ref>{{cite journal |last1=Tuoriniemi |first1=Juha |last2=Juntunen-Nurmilaukas |first2=Kirsi |last3=Uusvuori |first3=Johanna |last4=Pentti |first4=Elias |last5=Salmela |first5=Anssi |last6=Sebedash |first6=Alexander |title=Superconductivity in lithium below 0.4 millikelvin at ambient pressure |journal=Nature |volume=447 |issue=7141 |pages=187–9 |year=2007 |pmid=17495921 |doi=10.1038/nature05820 |bibcode=2007Natur.447..187T |s2cid=4430500 |url=https://zenodo.org/record/996565 |access-date=20 April 2018 |archive-url=https://web.archive.org/web/20190625233052/https://zenodo.org/record/996565 |archive-date=25 June 2019 |url-status=live}}</ref> and at higher temperatures (more than 9 K) at very high pressures (>20 GPa).<ref>{{Cite journal |doi=10.1126/science.1078535 |date=2002 |author=Struzhkin, V. V. |author2=Eremets, M. I. |author3=Gan, W |author4=Mao, H. K. |author5=Hemley, R. J. |title=Superconductivity in dense lithium |volume=298 |issue=5596 |pages=1213–5 |pmid=12386338 |journal=Science |bibcode=2002Sci...298.1213S |s2cid=21030510}}</ref> At temperatures below 70 K, lithium, like sodium, undergoes [[diffusionless transformations|diffusionless phase change transformations]]. At 4.2 K it has a [[rhombohedral crystal system]] (with a nine-layer repeat spacing); at higher temperatures it transforms to [[face-centered cubic]] and then [[body-centered cubic]]. At liquid-helium temperatures (4 K) the rhombohedral structure is prevalent.<ref name="overhauser">{{Cite journal |first=A. W. |last=Overhauser |title=Crystal Structure of Lithium at 4.2 K |doi=10.1103/PhysRevLett.53.64 |volume=53 |issue=1 |pages=64–65 |date=1984 |journal=Physical Review Letters |bibcode=1984PhRvL..53...64O}}</ref> Multiple allotropic forms have been identified for lithium at high pressures.<ref>{{cite journal |last1=Schwarz |first1=Ulrich |title=Metallic high-pressure modifications of main group elements |journal=Zeitschrift für Kristallographie |volume=219 |pages=376–390 |date=2004 |doi=10.1524/zkri.219.6.376.34637 |issue=6–2004 |bibcode=2004ZK....219..376S |s2cid=56006683}}</ref>

Lithium has a mass [[specific heat capacity]] of 3.58 kilojoules per kilogram-kelvin, the highest of all solids.<ref name="CRC">{{Cite book |author=Hammond, C. R. |title=The Elements, in Handbook of Chemistry and Physics |date=2000 |publisher=CRC press |isbn=978-0-8493-0481-1 |edition=81st}}{{page needed|date=December 2016}}</ref><ref>[https://web.archive.org/web/20140823211840/http://hilltop.bradley.edu/~spost/THERMO/solidcp.pdf SPECIFIC HEAT OF SOLIDS]. bradley.edu</ref> Because of this, lithium metal is often used in [[coolant]]s for [[heat transfer]] applications.<ref name="CRC" />