There are some exceptions to the trends of first and successive ionization energies. For each of the following pairs, explain which ionization energy would be higher:

(a) IE₁ of Ga or IE₁ of Ge

(b) IE₂ of Ga or IE₂ of Ge

(c) IE₃ of Ga or IE₃ of Ge

(d) IE₄ of Ga or IE₄ of Ge

(b) IE₂ of Ga > IE₂ of Ge

Explanation:

Electronic configuration of Ga is [Ar] 3d¹⁰4s²4p¹

Electronic configuration of Ge is [Ar] 3d¹⁰4s²4p²

After 1st ionisation, Ga becomes [Ar] 3d¹⁰4s² and becomes stable. Its

2 nd ionisation requires higher amount of ionisation energy. In case of Ge, there are 2 electrons in outermost orbital so it becomes stable after ionisation of 2 electrons.

a) IE1 of Germenium. ionization energy decreases down the group.

b) Here IE2 of Ga is higher because second valence electron of gallium is in s orbital whereas second valence electron of germenium is in p orbital.

c) IE3 of Ge is higher as this follows the trend.

d) IE4 of Ga is higher because the 4th valence electron of Ga is a core electron and the for Ge it is in s orbital and it takes higher energy to break a core electron than the orbital ones.