Question

How many valence electrons are in an atom of Magnesium?

Answer 1

Valence electron:

1. Valence electrons are electrons in the outermost shell of an atom.
2. Atoms with a full valence shell of electrons are the most stable.
3. They are determined by the electronic configuration of an atom.
4. Magnesium has an atomic number $=12$ so its electronic configuration is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2$
5. The outer shell $3\mathrm{s}$ is completely filled with $2$electrons.

Therefore, number of the valence electron in magnesium is $2$