Question

The energy of an atom or ion in the ground state is $-54.4eV$. It may be

• A. $H{e}^{+}$
• B. $L{i}^{2+}$
• C. hydrogen
• D. deuterium

Answer 1

The correct option is A $H{e}^{+}$

Energy of an atom or ion $=-13.6\frac{z^2}{n^2}$
Given: $\frac{54.\dot{4}}{13.6}=\frac{Z^2}{1}$ [$n=1$ for ground state]
$Z^2=4\Rightarrow Z=2$
So, $H{e}^{+2}$ is the ion with $Z=2.$