Which of the following is the electronic configuration of Cr?
Correct answer: B. [Ar] 3d5 4s1
- A. [Ar] 3d5 4s2
- B. [Ar] 3d5 4s1
- C. [Ar] 3d4 4s2
- D. [Ar] 3d6 4s0
Explanation
Chromium (Cr) has atomic number 24. Theoretically, the electronic configuration of Cr should be 1s2 2s2 2p6 3s2 3p6 3d4 4s2 (NOTE: [Ar] symbol denotes the electronic configuration for 1s2 2s2 2p6 3s3 3p6). However, in reality, one electron from 4s jumps to the 3d subshell so, that the configuration is [Ar] 3d5 4s1. This is because a half-filled d subshell, which is 3d5, is much more stable than 3d4, and atoms favor stability. Hence, option B is the correct answer.
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