Question

Which one of the following is the ground-state electron configuration of the Mg2+ ion?

Answer 1

Magnesium is located in period 3, group 2 of the periodic table, and has an atomic number equal to 12. This means that a neutral magnesium atom has 12 electrons that surround its nucleus.

When magnesium loses two of its electrons, it becomes the `Mg^(2+)` cation, which implies that the total number of electrons will decrease by 2.

As a result, the electron configuration of the `Mg^(2+)` cation must account for a total of 10 electrons.

`"Mg"^(2+): 1s^(2) 2s^(2) 2p^(6)`

The `Mg^(2+)` cation is isoelectronic with neon, `Ne`, and has a noble gas shorthand notation of

`"Mg"^(2+):["Ne"]`