Question

In $3^{rd}A$ group $Tl$ shows +$1$ oxidation state while other member shows +$3$ oxidation state due to :

• A. presence of lone pair of electron in $Tl$
• B. Inert pair effect
• C. Large Ionic radius of $Tl$ ion
• D. None of above

Answer 1

The correct option is B Inert pair effect

In 3rd A group Tl shows +1 oxidation state while other member shows +3 oxidation state due to inert pair effect. The inert pair effect is the tendency of the electrons in the outermost atomic S orbital to remain unionized or unshared in compounds of post-transition metals.

So in $Tl$ only outer electron 1.e $n{p}^1$ partcipate in chemical bonding where as the $n{s}^2$ do not particicpate in chemical bonding in a achemical reaction but other elements in that group do not show inert pair effect.

Hence option B is correct.