It's Elemental - The Element Lithium
Lithium is a member of group 1 of the periodic table and its only oxidation state is Li +. Its atomic mass varies because some minerals contain more of the higher isotope 7 Li or because the lower isotope 6Li has been extracted for use in nuclear weapons. 6 stable isotopes: 184Os, 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other natural isotope, 186Os, has an extremely long half-life (2×1015 years) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.56×1010 years) and is most often measured in an 187Os/188Os ratio.