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JAMB Chemistry 2000 Question 10

Question 10

Atomic Structure

The electron configuration of 22X2+ ion is

  1. A.1s22s22p63s23p64s23d2
  2. B.1s22s22p63s23p64s23d1
  3. C.1s22s22p63s23p6
  4. D.1s22s22p63s23p64s2
Show the answer and explanation

Answer: D (1s22s22p63s23p64s2)

Explanation

The ion X2+ has 22 − 2 = 20 electrons, and D is the only option with 20 electrons. (Strictly, a transition metal loses its 4s electrons first, giving 1s22s22p63s23p63d2, but that is not offered.)