# Q. 13.2  The three stable isotopes of neon: $_{10}^{20}\textrm{Ne},$ $_{10}^{21}\textrm{Ne}$ and $_{10}^{22}\textrm{Ne}$ have respective abundances of   $90.51\; ^{o}/_{o}$, $0.27\; ^{o}/_{o}$ and $9.22\; ^{o}/_{o}$. The atomic masses of the three isotopes are $19.99\; u, 20.99\; u \; \; and\; \; 21.99 \; u,$ respectively. Obtain the average atomic mass of neon.

$\\m= \frac{19.99\times 90.51+20.99\times 0.27+21.99\times 9.22}{100}\\m=20.1771u$