Mg-12 in Electron Configurations

Explanation:

The electronic configuration of an atom can be represented by either sublevel notation or using shell notations.

 Sublevel notations shows the sequence of filling electrons into the orbitals of the sublevels.

 Shell notations are used to denote the electrons in all orbitals of each energy level.

Element    Number of electrons    Sub-level notation      shell notation

  Mg                      12                          1s² 2s² 2p⁶ 3s²               2  8  2

first one is the correct answer