## Chemistry and Chemical Reactivity (9th Edition)

Their abundances are $48.02\%$ and $51.98\%$ respectively.
Europium's atomic weight is 151.96: $150.9197\times x+152.9212\times(1-x)=151.96$ solving for x: $x=0.4802$ Their abundances are $48.02\%$ and $51.98\%$ respectively.