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JAMB Chemistry 1985 Question 44

Question 44

Atomic Structure

The atomic number of an element whose cation, X2+, has the ground state electronic configuration 1s22s22p63s23p6 is

  1. A.16
  2. B.18
  3. C.20
  4. D.22
  5. E.24
Show the answer and explanation

Answer: C (20)

Explanation

The ion has 18 electrons. The atom lost 2 electrons to form X2+, so it had 20 electrons and an atomic number of 20 (calcium).