Atomic Mass Chemistry Example 1

Solution

1. 1
   Atomic mass is the weighted average of the masses of all naturally occurring isotopes of an element, measured in atomic mass units (amu).
2. 2
   Carbon has two stable isotopes: ${}^{12}\text{C}$ (mass 12, abundance 98.9%) and ${}^{13}\text{C}$ (mass 13, abundance 1.1%).
3. 3
   Weighted average: $12 \times 0.989 + 13 \times 0.011 = 11.87 + 0.14 = 12.01\,\text{amu}$.