Question

Element X has two naturally occurring isotopes, 10X (18.98 %
abundance) and 11X (81.02 % abundance). What is the atomic mass of
Element X?

Answer 1

We know the atomic mass

= (1/100)× Σ(% abundance ×mass no.) of isotopes

Given,

abundance of 10X isotope = 18.98 %

Mass no. = 10

abundance of 11X isotope = 81.02 %

Mass no = 11

So, atomic mass of X

= [(10×18.98)+(11×81.02)]/100

= 10.81

atomic mass of Element X = 10.81g/mol