d
\(1\) \(eV/atom\) \(=96.485 \times 10^{3} \,\mathrm{J} /\, \mathrm{mol}\)

\(\therefore 13.6\) \(eV/atom\) \(=13.6 \times 96.485 \times 10^{3}\, \mathrm{J} /\, \mathrm{mol}=1.312 \times 10^{6} \,\mathrm{J} /\,\mathrm{mol}^{-1}\)

Energy required to excite the electron from \(n_{1}\) to \(n_{2}\) is

\(\Delta E=13.6 \times Z^{2}\left(\frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}}\right)\)

\(=1.312 \times 10^{6} \times 1\left(\frac{1}{1^{2}}-\frac{1}{2^{2}}\right)\)

\(=1.312 \times \frac{3}{4} \times 10^{6}\)

\(=9.84 \times 10^{5}\, \mathrm{J}\, \mathrm{mol}^{-1}\)