Which of the following ions has an electron configuration different from the other?
Answer Details
The ion with an electron configuration different from the others is 17CI-. Chlorine (CI) has the electron configuration of 1s22s22p63s23p5 when neutral, but when it gains an electron to become an ion, it gains one more electron in the 3p subshell to have a full outer shell of 8 electrons, which gives it the electron configuration of 1s22s22p63s23p6. Oxygen (O), magnesium (Mg), and aluminum (AI) have electron configurations of 1s22s22p4, 1s22s22p63s2, and 1s22s22p63s23p1, respectively, when neutral. When they become ions, they either lose or gain electrons to achieve a full outer shell of 8 electrons for stability, which does not change their electron configuration in the same shell. Therefore, the correct answer is 17CI-.