Question

The atomic mass of lithium is 6.94, the naturally occurring isotopes are 6Li = 6.015121 amu, and 7Li = 7.016003 amu. Determine the percent abundance of each isotope.

Answer 1

amu is atomic mass unit or the proportion of the isotope existing in nature expressed in percentage. i.e. 6Li exist approximately 6.015% while 7Li exist 7.016%.

hope that helps.