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Q.
Variable oxidation state and degenerated orbital shows:
Punjab PMETPunjab PMET 2005Classification of Elements and Periodicity in Properties
Solution:
Variable oxidation state and degenerated orbital show by $d$-block elements. Variable oxidation state is the characteristic property of $d$-block elements. This is because both $((n-1) d$ and $n s$ electrons can take part in bond formation due to small energy difference between them.