Question

Which has maximum stability?

• A. $AsC{l}_3$
• B. $SbC{l}_3$
• C. $BiC{l}_3$
• D. Equal

Answer 1

The correct option is C $BiC{l}_3$

The inertness of s subshell electrons towards the bond formation is called inert pair effect or it can be said as the inactiveness of electrons present in outermost shell (i.e. $n{s}^2$) to get unpaired and involve in bond formation is called inert pair effect.

for example:

1) In 13th group, thallium can exhibit +1 and+3 oxidation states but it is stable in +1 oxidation state only due to inert pair effect

2) In 14th group , lead shows both +2 and +4 oxidation states but it is stable in +2 oxidation state due to inert pair effect.

Due to inert-pair effect
Stability of $A{s}^{3+}<S{b}^{3+}<B{i}^{3+}$