Magnesium (Mg)
Element 12 · alkaline earth metal · group 2, period 3
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
Magnesium Lewis dot structure
Magnesium has 2 valence electrons, so its Lewis symbol carries 2 dots: two single dots. The dots go one to a side before any of them pair up, so the unpaired ones show exactly how many bonds the atom tends to form. The ion has given those electrons away, which is why it is drawn in brackets with none.
Draw it in the Lewis structure generator →
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
What is the Lewis dot structure of magnesium?
The symbol Mg with 2 dots, one for each valence electron: two single dots. Dots go one to a side before any pair up, the same way electrons fill separate orbitals before sharing one. The Mg2+ ion is drawn in brackets with no dots, because it has lost them.
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.
Nearby elements
See the ionic charge of every element →