Question

A species having only one electron has ionization energy of $11810{mol}^{-1}$. The number of protons in its nucleus will be:

• A. $1$
• B. $2$
• C. $3$
• D. $4$

Answer 1

The correct option is C $3$

We have $E_n=\frac{-1312z^2}{n^2}kJ/mol$ for system with one $e^{-}$

$\therefore 11180=\frac{1312\times z^2}{1^2}$ ($n=1$, single electron)

$\Rightarrow z^2=\frac{11180}{1312}$

$\Rightarrow z\simeq 3$

Hence number of protons= $3$