Question

The known oxidation states for both $V$ and $CO$ are

• A. +2, +3, +4, +5
• B. +2, +3, +4, +5, +6
• C. +2, +3, +4
• D. +2, +3

Answer 1

Answer: (A)

Most of transition methods show variable valences or different oxidation states because of incomplete $d$ subshell.
The variable oxidation states are due to the participation of $ns$ and $(n-1)d$ electrons in bonding,
${}_{23}V$ shows $+2,+3,+4$, and $+5$ oxidation states
${}_{27}Co$ shows $+2+3+4$ oxidation states.
Therefore, known oxidation states for both $V$ and $Co$ are
$+2,+3,+4$ and $+5$