Question

Supposing the ionization energy of hydrogen atom is $640eV$. The shell having energy equal to $-40eV$ is :

• A. $n=2$
• B. $n=3$
• C. $n=4$
• D. $n=5$

Answer 1

Answer: (C)

Since $E_H=-{\left(IE\right)}^H\times \frac{Z^2}{n^2}$

$\therefore Z=1$

$\Rightarrow$ $n=\sqrt{\frac{\left({IE}_H\right)}{E_H}}=\sqrt{\frac{640}{40}}=2\times 2$

$\therefore n=4$