Question

Given that the percentage abundance of the isotope ${}_{10}{}^{20}\mathrm{Ne}$ is 90% and that of the isotope ${}_{10}{}^{22}\mathrm{Ne}$ is 10%, calculate the average atomic mass of neon.

Answer 1

Isotopes of Neon are ${}_{10}{}^{20}\mathrm{Ne}\mathrm{and}{}_{10}{}^{22}\mathrm{Ne}$ with 90% and 10% abundance, respectively.

$$\begin{gathered} \mathrm{average}\mathrm{atomic}\mathrm{mass}\mathrm{of}\mathrm{Neon}=20\times \left[\frac{90}{100}\right]+22\left[\frac{10}{100}\right] \\ =\frac{1800}{100}+\frac{220}{100} \\ =18.00+2.2 \\ =20.2u \end{gathered}$$