試題詳解

1. The element lithium (Li) exists as two stable isotopes, 6Li (isotopic mass = 6.200 amu) and 7Li (isotopic mass = 7.200 amu). Lithium has an atomic mass of 7.125 amu. What is the percent abundance of 7Li ?
(A) 7.5 %
(B) 22.3%
(C) 90.2%
(D) 92.5%
(E) none of these