Magnesium (Mg)

Element 12 · alkaline earth metal · group 2, period 3

Electron shells, 2 + 8 + 2. The outer shell is highlighted - it is the only one that takes part in bonding.

Magnesium is element 12, a alkaline earth metal in group 2 and period 3. Its electron configuration is [Ne] 3s2. That leaves 2 valence electrons in the outer shell, with the shells filling 2, 8, 2. Losing its 2 valence electrons is the shorter route to a full shell, so it carries a charge of +2.

12 protons
2 valence e−
+2
s-block

Properties

Atomic number	12
Symbol	Mg
Standard atomic weight	24.305 u
Group	2
Period	3
Block	s-block
Category	alkaline earth metal
Electron configuration	1s² 2s² 2p⁶ 3s²
Noble-gas notation	[Ne] 3s²
Electrons per shell	2, 8, 2
Valence electrons	2
Common ionic charge	+2
Electronegativity (Pauling)	1.31
Protons / electrons	12 / 12

Electron configuration of magnesium

Orbitals fill from the lowest energy upward. Writing that out for magnesium gives 1s² 2s² 2p⁶ 3s², which is 1s2 2s2 2p6 3s2 in plain text.

Everything up to Ne is the same as in that noble gas, so it is usually abbreviated to [Ne] 3s². The part outside the bracket is what does the chemistry.

Subshell	Electrons	Capacity
1s	2	2
2s	2	2
2p	6	6
3s	2	2

Magnesium ion charge

Magnesium commonly forms ions with a charge of +2.

It has 2 valence electrons, so it is 6 short of a full octet and 2 above an empty outer shell. An atom takes whichever route is shorter, which is why the charge comes out as it does.

Common questions

How many valence electrons does magnesium have?

Magnesium has 2 valence electrons. For groups 1 and 2 the count is the group number, and magnesium is in group 2.

What is the electron configuration of magnesium?

1s2 2s2 2p6 3s2, or [Ne] 3s2 written from the previous noble gas. Orbitals fill lowest energy first.

What is the charge of magnesium?

Magnesium commonly forms ions with a charge of +2. With 2 valence electrons it is 6 short of an octet and 2 above an empty shell, so it takes whichever route is shorter.

How many protons, electrons and neutrons does magnesium have?

A neutral magnesium atom has 12 protons and 12 electrons. Its standard atomic weight is 24.305, so the most common isotope has about 12 neutrons.

See the ionic charge of every element →

How this page was produced. The configuration was built by filling orbitals in energy order from atomic number 12 alone, not looked up. The shell counts, the valence count and the charge all follow from it. Nothing on this page is written per element.