Use the periodic table to answer the following question. How many valence electrons does magnesium (Mg) have?

Mg is in group 2 of the periodic table. The group determines the number of valence electrons an atom has. Groups 1-4 have that many. Groups 5-7 have 8-the group number. Group 8 has none as it is in the noble gas configuration with a full outer shell.

So, Mg has 2 valence electrons.