MDCAT Chemistry MCQ #965

Why does the 4s orbital fill before 3d orbitals in electron configuration?

MDCAT Chemistry MCQ #965

  1. Question 1

    Q1. Why does the 4s orbital fill before 3d orbitals in electron configuration?

    • A) Lower energy level for 4s
    • B) Greater electron shielding in 3d
    • C) Higher spin multiplicity in 4s
    • D) Stronger nuclear attraction for 4s

    Answer: Lower energy level for 4s

    Explanation: 4s has lower energy than 3d in filling order. Shielding (B) affects energy but doesn't reverse 4s/3d filling.