Question

How much energy is required to excite a hydrogen atom from its ground state to second excited state?

Answer 1

The energy of an electron in $n^{th}$ shell of a hydrogen atom is given as

$E=-13.6\times \frac{1}{n^2}eV$

Hence the energy required to excite it from $(1\to 3)$ is

$=13.6(\frac{1}{1^2}-\frac{1}{3^2})eV$

$=12.08eV$