Question

Energy of electron in first excited state of $H$-atom is:

• A. $-13.12$ x ${10}^{5}J/mol$
• B. $-3.28$ x ${10}^{5}J/mol$
• C. $13.12$ x ${10}^{3}J/mol$
• D. $3.28$ x ${10}^{2}J/mol$

Answer 1

The correct option is B $-3.28$ x ${10}^{5}J/mol$

The energy of an electron in the $n-th$ orbit of $H$-atom is given by,

$E_n=-13.12\times {10}^5\times \frac{1}{n^2}J$

For first excited state, $n=2$

$\Rightarrow E_n=\frac{-13.12\times {10}^5}{4}$

$\Rightarrow E_n=-3.28\times {10}^{5}J$