Question

If Aufbau rule is not followed in filling of sub orbitals, then block of the element will change in :

• A. K(19)
• B. Sc(21)
• C. V(23)
• D. Ni(28)

Answer 1

The correct option is A K(19)

If Aufbau rule is not followed,
electronic configuration is K:
1s${}^2$ 2s${}^2$ 2p${}^6$ 3s${}^2$ 3p${}^6$ 3d${}^1$.
Last electron is in 3d(instead of $4s$),
hence d block (but it is of $s$ block)
in all other cases valence electron doesnt changes its position so block doesnt changes in those cases.