The stability of +1 oxidation state among Al, Ga, In and Tl increases in the sequence:
Ga < In < Al < Tl
Al < Ga < In < Tl
Tl < In < Ga < Al
In < Tl < Ga < Al
As we learned in concept no
Inert pair effect -
The phenomenon in which outer shell s electrons (ns2) penetrate to (n-1) d-electrons and thus become closer to nucleus and are more effectively pulled by the nucleus
- wherein
This results in less availability of ns2 electrons pair for bonding or ns2 electron pair becomes inert.
The order of stability of +1 oscidation state is
This is on account of inert pair effect in which outer shell and electrons penetrate into (n-1) d electrons and thus become closer to nucleus and are therefore less available for bonding.
Option 1)
Ga < In < Al < Tl
This is incorrect option
Option 2)
Al < Ga < In < Tl
This is correct option
Option 3)
Tl < In < Ga < Al
This is incorrect option
Option 4)
In < Tl < Ga < Al
This is incorrect option