question_answer 33)

How much energy is required to ionise a H-atom if the electron occupies \[n=5\] orbit? Compare your answer with the ionisation enthalpy of H-atom (energy required to remove the electron from \[n=1\]orbit).

Answer:

\[\Delta E={{E}_{\infty }}-{{E}_{5}}\] =\[0-\left[ \frac{-{{Z}^{2}}}{{{n}^{2}}}\times 2.18\times {{10}^{-18}}\text{J} \right]\] \[=-\left[ \frac{-{{1}^{2}}}{{{5}^{2}}}\times 2.18\times {{10}^{-18}}\text{J} \right]\] \[=\frac{1\times 2.18\times {{10}^{-18}}}{25}=8.72\times {{10}^{-20}}J\] Ionisation enthalpy of hydrogen atom \[=2.18\times {{10}^{-18}}\text{J}\]