what is inert pair rule? please give a example toothank you in advance

Inert effect is the reluctance of valence s-shell electron in participating in the chemical bond formmation due to increase in effective nuclear charge while coming down the group. For example: In 13^thgroup(started from B and end to Tl), the +3 oxidation state is quite stable for lighter elements and Tl is quite stable for +1 oxidation state.

Dear student please read this important concept with more examples in a text-book.

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