Isotopes of lithium
From Wikipedia, the free encyclopedia
Lithium (Li)
Standard atomic mass: [6.941(2)] u
The isotopes of lithium include two stable isotopes, Lithium-6 and Lithium-7.
Contents |
[edit] Isotopes
[edit] Lithium-4
Lithium-4 contains 3 protons and one neutron. It is the shortest lived isotope of lithium. It decays by proton emission and has a half-life of 9.1×10-23 s. It can be formed as an intermediate in some nuclear fusion reactions.
[edit] Lithium-6
Lithium-6 is valued as a source material for tritium production and as a neutron absorber in nuclear fusion. Large amounts of lithium have been isotopically fractionated for use in nuclear weapons.
[edit] Lithium-7
Some of the material remaining from the production of Lithium-6, which is depleted in Lithium-6 and enriched in Lithium-7, is made commercially available, and some has been released into the environment. Relative lithium-7 abundances as high as 35.4% greater than the natural value have been measured in ground water from a carbonate aquifer underlying West Valley Creek, Pennsylvania (USA), down-gradient from a lithium processing plant. In depleted material, the relative Li-6 abundance may be reduced by as much as 80 percent of its normal value, giving the atomic mass a range from 6.94 u to more than 6.99 u. As a result, the isotopic composition of lithium is highly variable depending on its source. An accurate atomic mass cannot be given representatively for all samples.
[edit] Table
| nuclide symbol |
Z(p) | N(n) | isotopic mass (u) |
half-life | nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|
| excitation energy | |||||||
| 4Li | 3 | 1 | 4.02719(23) | 91(9)×10−24 s [6.03 MeV] | 2- | ||
| 5Li | 3 | 2 | 5.01254(5) | 370(30)×10−24 s [~1.5 MeV] | 3/2- | ||
| 6Li | 3 | 3 | 6.015122795(16) | STABLE | 1+ | [0.0759(4)] | 0.07714-0.07225 |
| 7Li | 3 | 4 | 7.01600455(8) | STABLE | 3/2- | [0.9241(4)] | 0.92275-0.92786 |
| 8Li | 3 | 5 | 8.02248736(10) | 840.3(9) ms | 2+ | ||
| 9Li | 3 | 6 | 9.0267895(21) | 178.3(4) ms | 3/2- | ||
| 10Li | 3 | 7 | 10.035481(16) | 2.0(5)×10−21 s [1.2(3) MeV] | (1-,2-) | ||
| 10m1Li | 200(40) keV | 3.7(15)×10−21 s | 1+ | ||||
| 10m2Li | 480(40) keV | 1.35(24)×10−21 s | 2+ | ||||
| 11Li | 3 | 8 | 11.043798(21) | 8.75(14) ms | 3/2- | ||
| 12Li | 3 | 9 | 12.05378(107)# | <10 ns | |||
[edit] Notes
- The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
- Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
- Commercially available materials may have been subjected to an undisclosed or inadvertent isotopic fractionation. Substantial deviations from the given mass and composition can occur.
- In depleted material, the relative Li-6 abundance may be reduced by as much as 80 percent of its normal value, giving the atomic mass a range from 6.94 u to more than 6.99 u.
- Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
- Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.
- Isotope 11 has a Nuclear halo of two weakly linked neutrons, thus explaining an important difference in the radius.
[edit] References
- Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
- Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
- Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
- Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
- National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
- David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.
| Isotopes of helium | Isotopes of lithium | Isotopes of beryllium |
| Index to isotope pages | ||
