posted by Annika .
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.
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.