What oxidation states does magnesium exhibit?

Magnesium shows only one stable oxidation state: +2. In its elemental form it is assigned 0 by convention. States such as +1 are not observed in stable compounds under normal conditions because the second ionization energy (1451 kJ/mol) is accessible alongside the first, driving full removal of both 3s electrons, and the energy released by lattice formation or hydration favors Mg²⁺ strongly over Mg⁺.

Why does magnesium not show a +1 oxidation state?

Although a +1 state is theoretically possible, the lattice energies and solvation energies for Mg²⁺ compounds far exceed those for hypothetical Mg⁺ compounds. The overall thermodynamic cycle strongly favors removing both valence electrons, so Mg⁺ compounds are not stable under normal conditions.

What is magnesium's electron configuration?

Ground state: 1s² 2s² 2p⁶ 3s², abbreviated as [Ne] 3s². When magnesium ionizes to Mg²⁺, both 3s electrons are removed, leaving the neon core 1s² 2s² 2p⁶.

What are the most common magnesium compounds?

The most common magnesium compounds include magnesium oxide (MgO), magnesium chloride (MgCl₂), magnesium sulfate (MgSO₄, also known as Epsom salt), magnesium hydroxide (Mg(OH)₂, milk of magnesia), and magnesium carbonate (MgCO₃). All feature Mg in the +2 oxidation state.

What are magnesium's ionization energies?

The first ionization energy (IE₁) of magnesium is 737.7 kJ/mol and the second (IE₂) is 1450.7 kJ/mol. The third ionization energy (IE₃) jumps dramatically to 7732.7 kJ/mol because it requires breaking into the stable neon core, confirming that +2 is the maximum accessible oxidation state.

How does magnesium differ from beryllium in its oxidation chemistry?

Both Be and Mg show only the +2 oxidation state, but their bonding character differs significantly. Beryllium's small ionic radius and high charge density lead to largely covalent bonds, while magnesium forms more truly ionic bonds. Mg²⁺ also coordinates more water molecules in solution (typically 6) compared to Be²⁺ (typically 4).

Magnesium Oxidation States

Reference and quiz tool for magnesium oxidation states: shows all known states (+2 primary), common compounds, electron configuration, and a self-test quiz.

Atomic # 12 Mg Magnesium

Atomic Mass

24.305 u

Group

2 (IIA)

Period

Block

s-block

Electronegativity

1.31 (Pauling)

Oxidation States

+2 only

Magnesium exhibits one stable oxidation state: +2. Its ground-state configuration is [Ne] 3s² — losing both valence 3s electrons gives the stable neon core. The ionization energy for a third electron (IE₃ = 7732.7 kJ/mol) is prohibitively large, making higher states inaccessible under ordinary conditions.

Oxidation State	Stability	Notes
+2	Stable	Universal oxidation state in all known stable magnesium compounds. Mg loses both 3s electrons to achieve the [Ne] configuration.
0	Elemental only	Assigned to pure magnesium metal by convention. Not a compound oxidation state.
+1	Not stable	Thermodynamically disfavored — lattice and solvation energies for Mg²⁺ far exceed those for Mg⁺, so Mg⁺ compounds disproportionate spontaneously.
+3 and above	Not observed	IE₃ = 7732.7 kJ/mol requires removing an electron from the neon core — energetically impossible under normal conditions.

Ionization Energies
IE₁ = 737.7 kJ/mol | IE₂ = 1450.7 kJ/mol | IE₃ = 7732.7 kJ/mol
The large jump from IE₂ to IE₃ (×5.3) confirms that +2 is the maximum oxidation state.

All stable magnesium compounds feature Mg in the +2 oxidation state. Because Mg²⁺ has a moderate ionic radius (0.72 Å), its compounds are predominantly ionic with relatively straightforward lattice structures.

Compound	Formula	Mg State	Notes
Magnesium Oxide	MgO	+2	Basic oxide; very high melting point (2852 °C); used as a refractory material.
Magnesium Chloride	MgCl₂	+2	Soluble ionic salt; found in sea water; used in de-icing and food processing.
Magnesium Sulfate	MgSO₄	+2	Epsom salt (heptahydrate); used in medicine and as a soil additive.
Magnesium Hydroxide	Mg(OH)₂	+2	Milk of magnesia; antacid and laxative; amphoteric with slight solubility.
Magnesium Carbonate	MgCO₃	+2	Magnesite mineral; used in gymnastics chalk and as a refractory.
Magnesium Nitrate	Mg(NO₃)₂	+2	Soluble salt; used as a fertilizer; decomposes on heating to MgO.
Magnesium Fluoride	MgF₂	+2	Low refractive index optical material; used in anti-reflection coatings.
Magnesium Sulfide	MgS	+2	Ionic solid; hydrolyzes in moist air; used in some phosphors.
Magnesium Bromide	MgBr₂	+2	Used as a Grignard reagent precursor in organic synthesis.
Magnesium Nitride	Mg₃N₂	+2	Formed when Mg burns in nitrogen; hydrolyzes readily.
Magnesium Acetate	Mg(CH₃COO)₂	+2	Soluble salt; used as a fixing agent in dyeing textiles.
Chlorophyll a	C₅₅H₇₂MgN₄O₅	+2	Biological pigment; Mg²⁺ chelated at the center of the porphyrin ring.

Ground State Configuration

Core — identical to He

Core — part of Ne shell

Valence electrons — lost on ionization to Mg²⁺

Notation

Full: 1s² 2s² 2p⁶ 3s²

Noble gas: [Ne] 3s²

Mg²⁺: [Ne] (1s² 2s² 2p⁶)

Ionization Steps

[Ne] 3s²

Neutral atom

Mg⁺

[Ne] 3s¹

Remove 1st valence electron — IE₁ 737.7 kJ/mol

Mg²⁺

[Ne]

Remove 2nd valence electron — IE₂ 1450.7 kJ/mol — stable noble-gas core

Mg³⁺

[He] 2s² 2p⁵

Break into Ne core — IE₃ 7732.7 kJ/mol — not accessible normally

Period 3 and d-orbitals: Magnesium sits in Period 3, where 3d orbitals exist but are much higher in energy for a low-charge +2 ion. Unlike transition metals, Mg does not use d orbitals in bonding, which limits it to the single +2 oxidation state.

Copied!

Summary

Magnesium (Mg) is an alkaline earth metal with atomic number 12. It exclusively adopts a +2 oxidation state in all stable compounds by losing its two 3s valence electrons to attain a neon-like noble-gas core. This page covers the electron configuration, ionization energies, key compounds such as MgO and MgCl₂, physical properties, and an interactive quiz to help students test their knowledge.

How it works

Switch between tabs — Oxidation States, Compounds, Electron Config, Physical Props — to explore different aspects.
The Oxidation States panel lists every known state with stability notes and ionization energy data.
The Compounds panel shows common magnesium compounds with their formulas and Mg oxidation state assignments.
The Electron Config panel walks through orbital filling and ionization steps visually.
The Quiz tab presents randomized multiple-choice questions about magnesium chemistry.
Click any compound formula to copy the value to your clipboard.

Use cases

Students studying Group 2 alkaline earth metals and oxidation state rules.
Chemistry teachers preparing reference material on magnesium.
Exam preparation for topics covering periodic table trends and redox chemistry.
Researchers needing a concise atomic and compound data reference for magnesium.
Self-testing with the built-in quiz before a chemistry test or exam.
Engineers or materials scientists referencing magnesium alloy chemistry basics.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu