Question

An element Is present in the earth's crust as isotopes of mass 107 u (55%) and 109 u (45%). The average atomic mass of the element is​

Answer 1

Average atomic mass is obtained as:

$\frac{107 * 55 + 109* 45}{100} = 107.9$

The formula is as follows:

$\frac{ m_{1} * percentage\ abundance + m_{2} * percentage\ abundance }{100}$