Editing Lithium (section)

=== Isotopes ===
{{Main|Isotopes of lithium}}
Naturally occurring lithium is composed of two stable [[isotope]]s, <sup>6</sup>Li and <sup>7</sup>Li, the latter being the more abundant (95.15% [[natural abundance]]).{{CIAAW2013}}<ref>{{NUBASE2020}}</ref> Both natural isotopes have anomalously low [[nuclear binding energy]] per nucleon (compared to the neighboring elements on the [[Periodic chart of the elements|periodic table]], [[helium]] and [[beryllium]]); lithium is the only low numbered element that can produce net energy through [[nuclear fission]]. The two lithium nuclei have lower binding energies per nucleon than any other stable nuclides other than [[hydrogen-1]], [[deuterium]] and [[helium-3]].<ref name="bind">[[:File:Binding energy curve - common isotopes.svg]] shows binding energies of stable nuclides graphically; the source of the data-set is given in the figure background.</ref> As a result of this, though very light in atomic weight, lithium is less common in the Solar System than 25 of the first 32 chemical elements.<ref name="Lodders2003" /> Seven [[radioisotope]]s have been characterized, the most stable being <sup>8</sup>Li with a [[half-life]] of 838 [[millisecond|ms]] and <sup>9</sup>Li with a half-life of 178&nbsp;ms. All of the remaining [[radioactive]] isotopes have half-lives that are shorter than 8.6&nbsp;ms. The shortest-lived isotope of lithium is <sup>4</sup>Li, which decays through [[proton emission]] and has a half-life of 7.6 × 10<sup>−23</sup> s.<ref name="nuclidetable">{{cite web |url=http://www.nndc.bnl.gov/chart/reCenter.jsp?z=104&n=158 |title=Interactive Chart of Nuclides |publisher=Brookhaven National Laboratory |author=Sonzogni, Alejandro |location=National Nuclear Data Center |access-date=6 June 2008 |url-status=live |archive-url=https://web.archive.org/web/20070723192118/http://www.nndc.bnl.gov/chart/reCenter.jsp?z=104&n=158 |archive-date=23 July 2007}}</ref> The <sup>6</sup>Li isotope is one of only [[Stable nuclide#Odd and even proton and neutron count|five stable nuclides]] to have both an odd number of protons and an odd number of neutrons, the other four stable [[Even and odd atomic nuclei#Odd proton, odd neutron|odd-odd nuclides]] being [[deuterium|hydrogen-2]], [[boron-10]], [[nitrogen-14]], and [[tantalum-180m]].<ref>{{cite book |last=Various |editor=Lide, David R. |year=2002 |title=Handbook of Chemistry & Physics |edition=88th |publisher=CRC |url=http://www.hbcpnetbase.com/ |access-date=2008-05-23 |isbn=978-0-8493-0486-6 |oclc=179976746 |archive-date=24 July 2017 |archive-url=https://web.archive.org/web/20170724011402/http://www.hbcpnetbase.com/}}</ref>

<sup>7</sup>Li is one of the [[primordial elements]] (or, more properly, primordial [[nuclide]]s) produced in [[Big Bang nucleosynthesis]].  A small amount of both <sup>6</sup>Li and <sup>7</sup>Li are produced in stars during [[stellar nucleosynthesis]], but it is further "[[Lithium burning|burned]]" as fast as produced.<ref>{{Cite journal |title=Lithium Isotopic Abundances in Metal-poor Halo Stars |date=2006 |journal=The Astrophysical Journal |doi=10.1086/503538 |volume=644 |issue=1 |pages=229–259 |author=Asplund, M. |bibcode=2006ApJ...644..229A |arxiv=astro-ph/0510636 |display-authors=1 |last2=Lambert |first2=David L. |last3=Nissen |first3=Poul Erik |last4=Primas |first4=Francesca |last5=Smith |first5=Verne V. |s2cid=394822}}</ref>    <sup>7</sup>Li can also be generated in [[carbon star]]s.<ref>{{Cite journal |title=Episodic lithium production by extra-mixing in red giants |bibcode=2000A&A...358L..49D |first1=P. A. |last1=Denissenkov |first2=A. |last2=Weiss |journal=Astronomy and Astrophysics |volume=358 |pages=L49–L52 |date=2000 |arxiv=astro-ph/0005356 }}</ref>  Additional small amounts of both <sup>6</sup>Li and <sup>7</sup>Li may be generated from solar wind, cosmic rays hitting heavier atoms, and from early solar system <sup>7</sup>[[Beryllium|Be]] radioactive decay.<ref>{{Cite journal |url=http://sims.ess.ucla.edu/PDF/Chaussidon_et_al_Geochim%20Cosmochim_2006a.pdf |doi=10.1016/j.gca.2005.08.016 |first1=M. |last1=Chaussidon |first2=F. |last2=Robert |first3=K. D. |last3=McKeegan |journal=Geochimica et Cosmochimica Acta |volume=70 |issue=1 |date=2006 |pages=224–245 |title=Li and B isotopic variations in an Allende CAI: Evidence for the in situ decay of short-lived <sup>10</sup>Be and for the possible presence of the short−lived nuclide <sup>7</sup>Be in the early solar system |bibcode=2006GeCoA..70..224C |archive-url=https://web.archive.org/web/20100718065257/http://sims.ess.ucla.edu/PDF/Chaussidon_et_al_Geochim%20Cosmochim_2006a.pdf |archive-date=18 July 2010}}</ref>

Lithium isotopes fractionate substantially during a wide variety of natural processes,<ref>{{Cite journal |date=2004 |first1=H. M. |last1=Seitz |first2=G. P. |last2=Brey |first3=Y. |last3=Lahaye |first4=S. |last4=Durali |first5=S. |last5=Weyer |title=Lithium isotopic signatures of peridotite xenoliths and isotopic fractionation at high temperature between olivine and pyroxenes |journal=Chemical Geology |volume=212 |issue=1–2 |doi=10.1016/j.chemgeo.2004.08.009 |pages=163–177 |bibcode=2004ChGeo.212..163S}}</ref> including mineral formation (chemical precipitation), [[metabolism]], and [[ion exchange]]. Lithium ions substitute for [[magnesium]] and iron in octahedral sites in [[clay]] minerals, where <sup>6</sup>Li is preferred to <sup>7</sup>Li, resulting in enrichment of the light isotope in processes of hyperfiltration and rock alteration. The exotic <sup>11</sup>Li is known to exhibit a [[Halo nucleus|neutron halo]], with 2 neutrons orbiting around its nucleus of 3 protons and 6 neutrons. The process known as [[atomic vapor laser isotope separation|laser isotope separation]] can be used to separate lithium isotopes, in particular <sup>7</sup>Li from <sup>6</sup>Li.<ref>{{Cite book |page=330 |title=Tunable Laser Applications |author=Duarte, F. J |author-link=F. J. Duarte |publisher=CRC Press |date=2009 |isbn=978-1-4200-6009-6}}</ref>

Nuclear weapons manufacture and other nuclear physics applications are a major source of artificial lithium fractionation, with the light isotope <sup>6</sup>Li being retained by industry and military stockpiles to such an extent that it has caused slight but measurable change in the <sup>6</sup>Li to <sup>7</sup>Li ratios in natural sources, such as rivers. This has led to unusual uncertainty in the standardized [[atomic weight]] of lithium, since this quantity depends on the natural abundance ratios of these naturally-occurring stable lithium isotopes, as they are available in commercial lithium mineral sources.<ref name="Coplen2002">{{cite journal |doi=10.1351/pac200274101987 |title=Isotope-abundance variations of selected elements (IUPAC Technical Report) |date=2002 |last1=Coplen |first1=T. B. |last2=Bohlke |first2=J. K. |last3=De Bievre |first3=P. |last4=Ding |first4=T. |last5=Holden |first5=N. E. |last6=Hopple |first6=J. A. |last7=Krouse |first7=H. R. |last8=Lamberty |first8=A. |last9=Peiser |first9=H. S.|last10=N.N. |journal=Pure and Applied Chemistry |volume=74 |issue=10 |page=1987 |display-authors=9 |doi-access=free}}</ref>

Both stable isotopes of lithium can be [[laser cooling|laser cooled]] and were used to produce the first quantum degenerate [[Bose–Einstein condensate|Bose]]–[[Fermionic condensate|Fermi]] mixture.<ref>{{Cite journal |last1=Truscott |first1=Andrew G. |last2=Strecker |first2=Kevin E. |last3=McAlexander |first3=William I. |last4=Partridge |first4=Guthrie B. |last5=Hulet |first5=Randall G. |date=2001-03-30 |title=Observation of Fermi Pressure in a Gas of Trapped Atoms |journal=Science |language=en |volume=291 |issue=5513 |pages=2570–2572 |doi=10.1126/science.1059318 |issn=0036-8075 |pmid=11283362 |bibcode=2001Sci...291.2570T |s2cid=31126288}}</ref>