Lithium has to naturally occurring isotopes: lithium-6 and lithium-7. If the average atomic mass of lithium is 6.941 amu, which isotope is the most abundant? How do you know

Question

Lithium has to naturally occurring isotopes: lithium-6 and lithium-7. If the average atomic mass of lithium is 6.941 amu, which isotope is the most abundant? How do you know?

Answer 1

The atomic mass of lithium-6 will be a number that is close to 6. The average mass of lithium -7 will be a number close to 7. The average atomic mass is a weighted average. This means that the percentage of each isotope may not contribute equally to the average. The atomic mass of lithium is 6.941 amu. This is close to 7. Therefore , lithium 7 must be more abundant than lithium 6.