The relative stability of +1 oxidation state of group 13 elements follows the order :
Ga < Al < In < TI
Al < Ga < TI < In
Al < Ga < In < TI
TI < In < Ga < Al
Oxidation state of boron family -
Boron show +3 covalence, this tendency decreases down the group, other members have +3 oxidation state form ionic compounds.
- wherein
Lower elements also show +1 ionic state due to inert pair effect. E.g. Tl+, Ga+
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.
Due to inert pair effect as we move down the group in 13th group lower oxidation state becomes more stable.
Ga < Al < In < TI
Option 2)Al < Ga < TI < In
Option 3)Al < Ga < In < TI
Option 4)TI < In < Ga < Al
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