Question

The element Magnesium (Mg) has an atomic number of 12. How many electrons are in its valence shell?

Answer 1

You should know how many electrons fit in each shell.

K 2
L 8
M 2

You can fit 8 electrons in the M shell but after filling up the first shells, there are only 2 electrons left. This means that there are 2 valence electrons.

Answer 2

Hey there!

First, know that a valence electron is an electron in an outer shell.  The Valence shell of the element magnesium contains a total of 2 Valence electrons.

Hope this helps you, good luck in Med-School!

~Fluerie