Question

Boron has two stable isotopes, ${}^{10}B\left(19\text{\%}\right)$ and ${}^{11}B\left(81\%\right)$. Calculate average atomic mass of boron in the periodic table.

• A. $10.8\text{u}$
• B. $10.2\text{u}$
• C. $11.2\text{u}$
• D. $10.0\text{u}$

Answer 1

The correct option is A $10.8\text{u}$

Average atomic mass Boron will be
$=\frac{19\times 10+81\times 11}{100}\text{u}=10.81\text{u}$