Isotopes of lithium

Isotopes of lithium (3Li)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
6Li [1.9%, 7.8%]
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 stable
7Li [92.2%, 98.1%]
Preview warning: Infobox Li isotopes: Abundance percentage not recognised "na=[92.2%, 98.1%]" cat#%
 stable
Significant variation occurs in commercial samples because of the wide distribution of samples depleted in 6Li.
Standard atomic weight Ar°(Li)

Naturally occurring lithium (3Li) is composed of two stable isotopes, lithium-6 (6Li) and lithium-7 (7Li), with the latter being far more abundant on Earth. Both of the natural isotopes have an unexpectedly low nuclear binding energy per nucleon (5332.3312(3) keV for 6Li and 5606.4401(6) keV for 7Li) when compared with the adjacent lighter and heavier elements, helium (7073.9156(4) keV for helium-4) and beryllium (6462.6693(85) keV for beryllium-9). The longest-lived radioisotope of lithium is 8Li, which has a half-life of just 838.7(3) milliseconds. 9Li has a half-life of 178.2(4) ms, and 11Li has a half-life of 8.75(6) ms. All of the remaining isotopes of lithium have half-lives that are shorter than 10 nanoseconds. The shortest-lived known isotope of lithium is 4Li, which decays by proton emission with a half-life of about 91(9) yoctoseconds (9.1(9)×10−23 s), although the half-life of 3Li is yet to be determined, and is likely to be much shorter, like 2He (helium-2, diproton) which undergoes proton emission within 10−9 s.

Both 7Li and 6Li are two of the primordial nuclides that were produced in the Big Bang, with 7Li to be 10−9 of all primordial nuclides, and 6Li around 10−13.[4] A small percentage of 6Li is also known to be produced by nuclear reactions in certain stars. The isotopes of lithium separate somewhat during a variety of geological processes, including mineral formation (chemical precipitation and ion exchange). Lithium ions replace magnesium or iron in certain octahedral locations in clays, and lithium-6 is sometimes preferred over 7Li. This results in some enrichment of 6Li in geological processes.

In nuclear physics, 6Li is an important isotope, because when it is bombarded with neutrons, tritium is produced.

Both 6Li and 7Li isotopes show nuclear magnetic resonance effect, despite being quadrupolar (with nuclear spins of 1+ and 3/2−). 6Li has sharper lines, but due to its lower abundance requires a more sensitive NMR-spectrometer. 7Li is more abundant, but has broader lines because of its larger nuclear spin. The range of chemical shifts is the same of both nuclei and lies within +10 (for LiNH2 in liquid NH3) and −12 (for Li+ in fulleride).[5]

  1. ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. ^ "Standard Atomic Weights: Lithium". CIAAW. 2009.
  3. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (4 May 2022). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. ^ Fields, Brian D. (2011). "The Primordial Lithium Problem". Annual Review of Nuclear and Particle Science. 61 (1): 47–68. arXiv:1203.3551. Bibcode:2011ARNPS..61...47F. doi:10.1146/annurev-nucl-102010-130445. S2CID 119265528.
  5. ^ "(Li) Lithium NMR".