Question

Which of the following elements has six unpaired electrons in observed electronic configuration?

• A. Fe (Z = 26)
• B. Cr (Z = 24)
• C. Cu (Z = 29)
• D. Mn (Z = 25)

Hint:

Half-filled and fully filled subshells give extra stability to atomic configurations.

Answer 1

The Correct Option is B

Step 1: Writing electronic configuration of chromium.
Chromium has an anomalous configuration:
\[ \mathrm{Cr: [Ar]\,3d^5\,4s^1} \]

Step 2: Counting unpaired electrons.
The five electrons in 3d orbitals are unpaired and one electron in 4s orbital is also unpaired.

Step 3: Total unpaired electrons.
\[ 5 + 1 = 6 \]

Step 4: Conclusion.
Therefore, chromium has six unpaired electrons in its observed electronic configuration.