Electronic configuration of chromium is:
Show Hint
- $[Ar]~3d^4 4s^1$
- $[Ar]~3d^4 4s^2$
- $[Ar]~3d^5 4s^1$
- $[Ar]~3d^5 4s^2$
The Correct Option is C
Solution and Explanation
Chromium (Cr) has an atomic number of 24. It is an exceptional case in the Aufbau principle of electron filling.
Step 2: Meaning
Half-filled and fully filled d-subshells offer extra stability due to symmetry and higher exchange energy.
Step 3: Analysis
The expected configuration for $Z=24$ based strictly on the Aufbau principle is $[Ar]~3d^4 4s^2$.
However, by shifting one electron from the 4s orbital to the 3d orbital, chromium achieves a $3d^5$ configuration.
This exactly half-filled d-subshell is far more thermodynamically stable.
Step 4: Conclusion
Therefore, the actual ground-state electronic configuration becomes $[Ar]~3d^5 4s^1$.
Final Answer: (C)
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