Question

The ionisation energy of the hydrogen atom is $13.6eV$. The energy needed to ionise a hydrogen atom which is in its second excited state is?

• A. $13.6eV$
• B. $10.2eV$
• C. $3.4eV$
• D. $1.5eV$

Answer 1

Answer: (D)

$1.5eV$

The ionization energy of the hydrogen atom is $13.6eV$ The energy needed to ionize a hydrogen atom which is in its second excited state $(n=3)$ is

$I.E=\frac{13.6}{n^2}=\frac{13.6}{3^2}=1.5eV$

Hence, the correct option is $D$