Question

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

NCERT Class XII
Chemistry - Main Course Book I

Chapter 2. Structure of Atom

Answer 1

n = 5 shell O  in the atom.

Ionization energy enthalpy of Hydrogen atom Z = 1, n = 1, to remove electron from 1S orbital... = 13.6 eV

Ionization energy = E = $\frac{Z^2}{n^2}*13.6\ eV=\frac{1^2}{5^2}13.6=0.544\ eV$

The ionization energy is inversely proportional to the square of n... so it is 1/25 th or 4% of the ionization energy of Hydrogen atom for the electron in K orbit.