Which of the following is the electronic configuration of an alkali earth metal of 3rd period?

[Ne] 3s¹

[Ne] 3s²

[Ne] 3s² 3p¹

[Ne] 3s² 3p² 3px¹

Alkaline earth metals: These elements have two valence electrons in their outermost s orbital.

3rd period: In the third period, the outermost shell is the 3rd shell.

Therefore, the electronic configuration of an alkaline earth metal in the 3rd period is [Ne] 3s².