Question

The number of occupied sub-shells in Cr${}^{3+}$ ion is:

• A. 3
• B. 4
• C. 5
• D. 6

Answer 1

The correct option is D 6

The sub-shell electronic configuration of
Cr 1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁵4s¹

Cr³⁺ 1s², 2s², 2p⁶, 3s², 3p⁶, 3d³

Therefore the number of sub-shells is 6( 1s,2s.2p,3s,3p,3d).