Q. In III A group, $Tl$ (thalium,) shows +1 oxidation state while other members show +3 oxidation state, why?
A) Presence of lone electron in $Tl$
B) Insert pair effect
C) Large ionic radius of $Tl$ ion
D) None of the above
Explanation
(b)
In III group, Tl (thalium) show+1 oxidation state due to inert pair effect. The outer shell‘s’ electrons $(ns^{2})$ penetrate to $(n - 1)d$ electrons and thus, become closer to nucleus and are more effectively pulled towards the nucleus. This results in less availability of $ns^{2}$ electron pair for bonding or $ns^{2}$ electron pair becomes inert.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.