Class 11-science Answered

Inert pair effect: The tendency of ns² electron pair to participate in bond formation decreases with increase in atomic size. Within a group the higher oxidation state becomes less stable with respect to the lower oxidation state as the atomic number increases. This trend is called inert effect.

In other words the inertness of the inner core ns electrons in the participation of chemical bonding is called the inert pair effect.

Oxidation state:  The sum of negative and positive charges in an atom, which indirectly indicates the number of electrons it has accepted or donated.