Magnesium (Mg)

Magnesium properties

Atomic number

12

Atomic mass

24.305 u

Category

Alkaline earth metal

Group

2

Period

3

Block

s-block

State at room temp.

Solid

Electronegativity

1.31

Melting point

923 K (649.8 °C)

Boiling point

1,363 K (1,089.8 °C)

Density

1.738 g/cm³

Valence electrons

2

Common charges

+2

Oxidation states

+2

Atomic radius

173 pm

Ionization energy

7.646 eV

Electron affinity

—

Radioactive

No, has stable isotopes

Discovered

1755

Magnesium electron configuration

The electron configuration of Magnesium (Mg) is [Ne] 3s2. Its 12 electrons are arranged in shells as 2, 8, 2.

Protons, neutrons and electrons in Magnesium

A neutral Magnesium atom has 12 protons and 12 electrons. Most Magnesium atoms have about 12 neutrons: the atomic mass rounded to 24, minus the atomic number 12.

Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass

How many valence electrons does Magnesium have?

2

Magnesium has 2 valence electrons in its outermost shell, shell 3. These are the electrons involved in chemical bonding.

See every element: Periodic table with valence electrons

Magnesium orbital diagram

Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations

Molar mass of Magnesium

24.305 g/mol

One mole of Magnesium atoms (6.022 × 10²³ atoms) has a mass of 24.305 grams. Use this value to convert between grams and moles.

Compounds containing Magnesium

Magnesium facts

• A chlorophyll molecule has a single magnesium atom at its center, so every green plant depends on magnesium to capture sunlight.
• Burning magnesium gives off a dazzling white light, and water makes a magnesium fire worse because the hot metal reacts with it to release hydrogen.
• Magnesium (Mg) has atomic number 12 and is a solid at room temperature. It was discovered in 1755.

Position in the periodic table

Magnesium is element 12, in period 3 and group 2 of the periodic table, in the s-block.

All alkaline earth metals

Uses of Magnesium

Magnesium is the lightest structural metal, so its alloys are used for car parts, laptop and camera bodies, and power tools. It is also added to aluminum to strengthen drink cans and other products, and it is used to remove sulfur from steel and to extract titanium from its ore. Magnesium compounds appear in antacids, in laxatives such as milk of magnesia, in Epsom salt and in heat-resistant furnace linings.

Who discovered Magnesium?

Scottish chemist Joseph Black recognized magnesium as an element in 1755, after showing that magnesia (magnesium oxide) is different from lime. Humphry Davy first isolated the metal in 1808, using electrolysis.

Where does the name come from?

Magnesium is named after magnesia, a white magnesium compound whose name comes from Magnesia, a district of Thessaly in Greece. Several minerals from that region were known by the name magnesia.

Discovery timeline