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Question 860001
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d- and f-Block Elements: Electronic configuration MCQ

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Electronic configurationEasyQuestion 860001

Question

Which of the following is NOT an exception to Aufbau principle for 3d metals?
  1. A
    Ni (d⁸s²)
    Correct
  2. B
    Cr (d⁵s¹)
  3. C
    Cu (d¹⁰s¹)
  4. D
    Mo (d⁵s¹)

Correct answer

Ni (d⁸s²)

Explanation

Cr: [Ar]3d⁵4s¹ (not 3d⁴4s²) — extra stability of half-filled d. Cu: [Ar]3d¹⁰4s¹ (not 3d⁹4s²) — extra stability of fully-filled d. Ni: [Ar]3d⁸4s² — no exception, follows Aufbau as expected.

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