WAEC Chemistry 2018 Objective — Question 44
Question 44 of 50 from the West African Examinations Council (WAEC) Chemistry 2018 Objective paper, with the correct answer and a full explanation.
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Which of the following electron configurations represents the transition element chromium (₂₄Cr)?
- A. 1s²2s²2p⁶6 3s²3p⁶6 4s²3d⁴
- B. 1s²2s²2p⁶6 3s²3p⁶6 4s²3d⁶
- C. 1s²2s²2p⁶6 3s²3p⁶6 4s¹3d⁵Correct
- D. 1s²2s²2p⁶6 3s²3p⁶6 4s²3d⁵
Explanation
Chromium is an exception to the normal filling order: its actual configuration is [Ar]4s¹3d⁵ (one electron shifts from 4s to 3d for a more stable half-filled d-subshell).
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