WAEC Chemistry 2021 Objective — Question 38
Question 38 of 50 from the West African Examinations Council (WAEC) Chemistry 2021 Objective paper, with the correct answer and a full explanation.
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38. The following ions have the same electron configuration except
- A. Cl⁻Correct
- B. O2-
- C. Mg2+
- D. Al3+
Explanation
Cl⁻ has 18 electrons (1s²2s²2p⁶3s²3p⁶), while O2-, Mg2+, and Al3+ each have 10 electrons (1s²2s²2p⁶) — Cl⁻ is the exception.
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