Editing Period 2 element (section)

===Lithium===
{{main article|Lithium}}
[[File:Lithium paraffin.jpg|thumb|left|150px|Lithium metal floating on paraffin oil]]

Lithium (Li) is an [[alkali metal]] with atomic number 3, occurring naturally in [[Isotopes of lithium|two isotopes]]: <sup>6</sup>Li and <sup>7</sup>Li. The two make up all natural occurrence of lithium on Earth, although [[Isotopes of lithium|further isotopes]] have been synthesized. In [[ionic compound]]s, lithium loses an [[electron]] to become positively charged, forming the [[cation]] Li<sup>+</sup>. Lithium is the first alkali metal in the periodic table,<ref group="note">Hydrogen is occasionally referred to as an alkali metal, although this is rare.</ref> and the first metal of any kind in the periodic table.<ref group="note">See note 1.</ref>  At [[standard temperature and pressure]], lithium is a soft, silver-white, highly reactive [[metal]]. With a [[density]] of 0.564 g⋅cm<sup>−3</sup>, lithium is the lightest metal and the least dense solid element.<ref name=weli>[http://www.webelements.com/lithium/ Lithium] at WebElements.</ref>

Lithium is one of the few elements [[Big Bang nucleosynthesis|synthesized]] in the [[Big Bang]].
Lithium is the 31st most abundant element on earth,<ref name=krebs>{{cite book | last = Krebs | first = Robert E. | year = 2006 | title = The History and Use of Our Earth's Chemical Elements: A Reference Guide | url = https://archive.org/details/historyuseourear00kreb_356 | url-access = limited | publisher = Greenwood Press | location = Westport, Conn. | isbn = 0-313-33438-2 | pages = [https://archive.org/details/historyuseourear00kreb_356/page/n71 47]–50}}</ref> occurring in concentrations of between 20 and 70 ppm by weight,<ref name=kamienski/> but due to its high reactivity it is only found naturally in [[Chemical compound|compounds]].<ref name=kamienski>Kamienski et al. "Lithium and lithium compounds". ''Kirk-Othmer Encyclopedia of Chemical Technology''. John Wiley & Sons, Inc. Published online '''2004'''. {{doi|10.1002/0471238961.1209200811011309.a01.pub2}}</ref>

Lithium [[Salt (chemistry)|salts]] are used in the pharmacology industry as [[Mood stabilizer|mood stabilising]] [[Medication|drugs]].<ref>{{cite journal
| title = Lithium salts in the treatment of psychotic excitement
| author = Cade J. F. J.
| journal = Medical Journal of Australia
| year = 1949
| volume = 2 |pmid=18142718
| pmc = 2560740
| issue = 10
| pages = 349–52
| url =https://www.who.int/docstore/bulletin/pdf/2000/issue4/classics.pdf | doi = 10.1080/j.1440-1614.1999.06241.x
}}</ref><ref>{{cite journal
| title =Lithium treatment for bipolar disorder
|author1=P. B. Mitchell |author2=D. Hadzi-Pavlovic | journal = Bulletin of the World Health Organization
| year = 2000
| volume = 78
| issue =4
| pages = 515–7 |pmid=10885179
| url =https://www.who.int/docstore/bulletin/pdf/2000/issue4/classics.pdf | pmc =2560742}}</ref> They are used in the treatment of [[bipolar disorder]], where they have a role in treating [[depression (mood)|depression]] and [[mania]] and may reduce the chances of [[suicide]].<ref>{{cite journal |vauthors=Baldessarini RJ, Tondo L, Davis P, Pompili M, Goodwin FK, Hennen J |date=October 2006 |title=Decreased risk of suicides and attempts during long-term lithium treatment: a meta-analytic review |journal=Bipolar Disorders |volume=8 |issue=5 Pt 2 |pages=625–39 |pmid=17042835 |doi=10.1111/j.1399-5618.2006.00344.x|doi-access=free }}</ref> The most common compounds used are [[lithium carbonate]], Li<sub>2</sub>CO<sub>3</sub>, [[lithium citrate]], Li<sub>3</sub>C<sub>6</sub>H<sub>5</sub>O<sub>7</sub>, [[lithium sulphate]], Li<sub>2</sub>SO<sub>4</sub>, and [[lithium orotate]], LiC<sub>5</sub>H<sub>3</sub>N<sub>2</sub>O<sub>4</sub>·H<sub>2</sub>O. Lithium is also used in [[lithium battery|batteries]] as an [[anode]] and its [[alloy]]s with [[aluminium]], [[cadmium]], [[copper]] and [[manganese]] are used to make high performance parts for [[aircraft]], most notably the [[Space Shuttle external tank|external tank]] of the [[Space Shuttle]].<ref name=weli/>