Question

The electronic configuration of an element is $1s^{2}2s^{2}2p^{6}3s^{2}3d^{5}4s^1$. This represents its

• A. Excited state
• B. Ground state
• C. Cationic form
• D. Anionic form

Answer 1

Answer: (B)

${}_{24}Cr=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{5}4s^1$
This is the ground state electronic configuration for chromium. There is only one electron in the $4s$ orbital because $d^5$ is a more stable half-filled configuration. Reasons for the stability of the halffilled and fully filled orbitals are symmetry and exchange energy