Question

The ionisation potential of hydrogen atoms is $13.6eV$. How much energy need to be supplied to ionise the hydrogen atom in the first excited state?

• A. $13.6eV$
• B. $27.2eV$
• C. $3.4eV$
• D. $6.8eV$

Answer 1

The correct option is C $3.4eV$

Ionisation energy of $nth$ state $=-E_n$
For the first excited state, $n=2$
and energy in that state is, $\frac{13.6}{2^2}eV=\frac{13.6}{4}eV$
$=3.4eV$.