:nitrogen has two isotopes, n-14 and n-15, with atomic masses of 14.00031 amu and 15.001 amu, respectively. what is the percent abundance of n-15?

The atomic mass of an element is a weighted average of its isotopes in which the sum of the abundance of each isotope is equal to 1 or 100%.

Let fraction of N-15 be x
then fraction of N-14 = 1-x 

Formula for Calculating Isotope:



on calculation:

x = 0.006403
so, % = 0.006403 x 100  =  0.6403 %

What? i don’t understand