Question

An element has two naturally-occurring isotopes. The mass numbers of these isotopes are 115.00 u and 117.00 u, with natural abundances of 25% and 75%, respectively. Calculate its average atomic mass. Report your answer to 2 decimal places.

Answer 1

$(115.00)(0.25)+(117.00)(0.75)=\boxed{116.50 \text{ u}}$