Question

The energy of an electron in an excited hydrogen atom is $ -3.4\,eV $ . Its angular momentum is

• A. $ 3.72\times 10^{-34}J-s$
• B. $2.11 \times 10^{-34}J-s$
• C. $1.57 \times 10^{-34}J-s$
• D. $1.11 \times 10^{-34}J-s $

Answer 1

Answer: (B)

Energy of electron in nth energy level in hydrogen atom
$=-\frac{136}{n^{2}} eV$
Here, $-\frac{13.6}{n^{2}}=-3.4\, eV$
So, $n=2$
Angular momentum from Bohrs principle
$=n \frac{h}{2 \pi}$
$=\frac{2 \times 6.626 \times 10^{-34}}{2 \times 314}$
$=2.11 \times 10^{-34} J - s$