Write down electronic configuration of the element having atomic number 21. name two other elements of the series to which this element belongs, why do they belong to the same series?

Explanation

Electronic configuration of the element (Atomic number=21):`1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(1)4s^(2)`
From the electronic configuration. It can be said that the element belongs to the first transition series at its 3d-orbital is partially filled. two other elements belonging to this series are Cr(24) and Mn(25). the 3d-robitals of these elements are also partially filled. their electronic configuration are-
`Cr:1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(5)4s^(1)`
`Mn:1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(5)4s^(2)`.