Question

Energy of an electron for hydrogen in $n^{th}$ orbit $E_n=-\frac{313.6}{n^2}$ kcal/mol. Find the value of 'n', if the energy of electrons in a certain orbit is - 19.6kcal/mol.

• A. n = 4
• B. n = 3
• C. n = 2
• D. n = 5

Answer 1

The correct option is A n = 4

We know, energy of the electron in $n^{th}$ orbit is $E_n=-R_H\times \frac{Z^2}{n^2}$ where $R_H$ is the rydberg energy constant.
Value of $E_n$ is given as -45.64 kcal/mol. Equating,
$-19.6=-\frac{313.6}{n^2}$ [ Z = 1 for hydrogen]
On solving, we get $n^2$ = 16
So, n = 4