Question

What will be the angular momentum of an electron, in a hydrogen atom, if its energy is $1.5\text{eV}$?

• A. $1.05\times {10}^{-34}\text{J-s}$
• B. $2.1\times {10}^{-34}\text{J-s}$
• C. $3.16\times {10}^{-34}\text{J-s}$
• D. $-2.1\times {10}^{-34}\text{J-s}$

Answer 1

The correct option is C $3.16\times {10}^{-34}\text{J-s}$

Energy of electron in H-atom $E_n=\frac{-13.6}{n^2}\left(\text{in eV}\right)$
$\Rightarrow -1.5=\frac{-13.6}{n^2}$

$\Rightarrow n=3$

Now, angular momentum is given by,
$L=\frac{nh}{2\pi }=\frac{3\times 6.63\times {10}^{-34}}{2\times 3.14}=3.16\times {10}^{-34}\text{J-s}$

Hence, $\left(C\right)$ is the correct answer.

Why this Question? This question is based on concept of angular momentum.