What is the ground state configuration of a magnesium atom?

Answer: 2-8-2

Explanation: look at the regents chemistry reference table (easiest way). If you understand what subshells are then you should know (or not) that S subshells only contain 2 electrons and the first shell only has one orbital (increases as the shells do). The second shell contains S and P (# of ē maxed at 6) subshells and the third shell has S, P, D (# of ē maxed at 10). The electron configuration for ground state would then be: 1s² 2s² 2p^6 3s²