Question

The energy of an electron in H atom is $-3.4eV$. If the angular momentum of the electron is $x\times {10}^{-34}Jse{c}^{-1}$, then $x$ is:

• A. 2.3
• B. 2.1
• C. 3.1
• D. 3.3

Answer 1

Answer: (B)

2.1

Use the formula,

Energy, $E=-13.6eV\times \frac{Z^2}{n^2}$

For hydrogen, $Z=1$ and $E=-3.4eV$

therefore, $n=2$

Angular momentum (mvr)$=n\frac{h}{2\pi }$$=\frac{2\times 6.626\times {10}^{-34}}{2\times 3.14}$$=2.1\times {10}^{-34}Jse{c}^{-1}$

$\Rightarrow x=2.1$