WAEC Chemistry 2011 Objective — Question 4
Question 4 of 50 from the West African Examinations Council (WAEC) Chemistry 2011 Objective paper, with the correct answer and a full explanation.
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Which of the following ions has the electron configuration 2, 8, 8?
- A. A. Na⁺
- B. B. Mg²⁺
- C. C. F⁻
- D. D. Cl⁻Correct
Explanation
11Na = 2,8,1 → Na⁺ = 2,8 (one electron lost). 12Mg = 2,8,2 → Mg²⁺ = 2,8 (two electrons lost). 9F = 2,7 → F⁻ = 2,8 (one electron gained). 17Cl = 2,8,7 → Cl⁻ = 2,8,8 (one electron gained), matching the required configuration.
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