Question

The energy needed to excite a hydrogen atom from its ground state to its third excited state is :

• A. $12.1eV$
• B. $10.2eV$
• C. $0.85eV$
• D. $12.75eV$

Answer 1

Answer: (C)

$0.85eV$

The required energy for excite a hydrogen atom from its ground state to its third excited state is:

$E_n=-\frac{13.6}{n^2}{Z}^2$

where $n=1$ for ground state and $n=4$ for third excited state, and $Z=1$ for hydrogen.

$E_n=-\frac{13.6}{4^2}{1}^2$

$E_n=0.85eV$

Hence the correct option is C.