WAEC - Chemistry (2012 - No. 3)
Which of the following ions has an electron configuration different from the other?
17CI-
8O2-
12Mg2+
13AI3+
Maelezo
\(_{17}\)Cl\(^-\) = 18 electrons = 2, 8, 8
\(_{12}\)Mg\(^{2+}\), \(_{8}\)O\(^{2-}\) and \(_{13}\)Al\(^{3+}\) all have 10 electrons = 2, 8.