Question

there are two isotopes of an element with atomic mass z. heavier one has atomic mass (z+2) an lighter one has (z-1), then abundance of lighter one is

Answer 1

Abundance of an isotope can be calculated as follows :

Let abundance of isotope with atomic mass Z+2 is x

Then abundance of isotope Z-1 is 1-x

(Z+2) x + (Z-1)(1-x) = Z

Solving we get

x=1/3

Therefore abundance of Z+2 is = (1/3)*100=33.33 %

And abundance of Z-1 is = 1-33.33 =67.66 %

Therefor isotope with atomic mass Z-1 is higher in % abundance.