Element 12 · Alkaline earth metal
Magnesium (Mg) — Element 12
Magnesia, Greece
Magnesium (Mg) is an alkaline earth metal in Period 3, Group 2 of the periodic table with atomic number 12, standard atomic weight 24.305 u, and ground-state electron configuration [Ne] 3s². At standard temperature and pressure it is classified as a solid with 2 valence electrons and common oxidation states +2.
Alloys, fireworks, chlorophyll
What are the atomic properties and physical constants of Magnesium?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 12
- Standard atomic mass
- 24.305 u
- Chemical family
- Alkaline earth metal
- Ground-state configuration
- [Ne] 3s²
- Electrons per shell
- 2, 8, 2
- Valence electrons
- 2
- Common ion charges / oxidation states
- +2
- Phase at STP
- Solid
- Pauling electronegativity
- 1.31 Pauling
- First ionization energy
- 738 kJ/mol
- Atomic radius
- 145 pm
- Melting point
- 650 °C
- Boiling point
- 1,090 °C
- Discovery year
- 1755
- Table coordinate
- Period 3, Group 2
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Magnesium’s shells?
A neutral Magnesium atom contains 12 electrons distributed across 3 occupied principal energy shells ([Ne] 3s²). The table below compares Magnesium’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in Mg | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 8 e⁻ | 8 e⁻ |
| n = 3 | M | 2 e⁻ | 18 e⁻ |
Frequently Asked Questions about Magnesium (Mg)
What is the atomic mass and atomic number of Magnesium (Mg)?
Magnesium (Mg) has atomic number Z = 12 (12 protons in its nucleus) and an IUPAC standard atomic weight of 24.305 u. It sits in Period 3, Group 2 and is classified as an alkaline earth metal.
What is the ground-state electron configuration of Magnesium?
The neutral ground-state electron configuration of Magnesium (Z = 12) is [Ne] 3s². Across its 3 occupied principal shells (n = 1 to n = 3), the electrons per shell are 2, 8, 2, with 2 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Magnesium?
Magnesium commonly forms +2 oxidation states or ion charges in compounds. Its Pauling electronegativity is 1.31 and its first ionization energy is 738 kJ/mol.
When was Magnesium discovered and what is it used for?
Magnesium was discovered in 1755 (Magnesia, Greece). Alloys, fireworks, chlorophyll
How does Magnesium compare to neighboring elements?
Other alkaline earth metal elements: