Magnesium Oxide(MgO) Properties (25 Facts You Should Know)

Magnesium oxide, known as magnesia, is a white-colored hygroscopic solid. Let us discuss the physical and chemical properties of magnesium oxide.

Magnesium oxide is produced due to the calcination of magnesium hydroxide [Mg(OH)₂] and magnesium carbonate (MgCO₃) and is soluble in acid and ammonia but insoluble in ethanol. It is one type of Mg supplement in the human body to prevent many diseases.

This article explains the IUPAC name, radius, polarity, magnetic behavior, color, odor melting, and boiling point of magnesium oxide in detail.

Magnesium Oxide IUPAC Name

The IUPAC (International Union of Pure and Applied Chemistry) name of magnesium oxide is magnesium oxide itself.

Magnesium Oxide Chemical Formula

Magnesium oxide has the chemical formula MgO.  

Magnesium Oxide CAS Number

MgO has the CAS registry number (authentic numeric identifier which can contain up to 10 digits) 1309-48-4.

Magnesium Oxide Chem Spider ID

MgO has the ChemSpider (ChemSpider is a free chemical structure database) ID 14108.

Magnesium Oxide Chemical Classification

• MgO can be chemically classified as an inorganic crystal compound and hygroscopic in nature.
• MgO can be chemically classified as alkaline or basic (lewis base).
• MgO can be chemically classified as an ionic compound.

Magnesium Oxide Molar Mass

The molar mass of MgO is 40.304 g. This molar mass is obtained from the summation of the molar mass of magnesium metal and oxygen which are 24.305 g/mole and 15.999 g/mole respectively.

Magnesium Oxide Color

Pure MgO is a white solid crystalline or powdered compound.

Magnesium Oxide Viscosity

MgO shows maximum viscosity of 1088 mPa.s and this is measured for the slag with 13.6% MgO.

Magnesium Oxide Molar Density

The molar density of MgO is 0.09 mol/cm³ because it has a density of 3.60 g/cm³ because the molar mass of 40.304 g/mol.

Magnesium Oxide Melting Point

MgO has a melting point of 2852⁰ C or 5166⁰ F. It shows a high melting point because the lattice of MgO is held by the strong ionic interaction between Mg²⁺ and O^2- ion.

Magnesium Oxide Boiling Point

The boiling point of MgO is 3600⁰ C or 6510⁰ F.

Magnesium Oxide state at Room Temperature

At room temperature, MgO is an ionic solid due to its high boiling and melting point.

Magnesium Oxide Ionic Bond

MgO is an ionic compound having 2 ions, Mg²⁺ and O^2-. Magnesium donates its 2 valence electrons from its 3s orbital to the 2p orbital of oxygen. After this donation and acceptance, Mg becomes Mg²⁺ and O becomes O^2-.

Magnesium Oxide Ionic Radius

In MgO, the ionic radius of magnesium ion (Mg²⁺) and oxide (O^2-) ion is 0.65 A⁰ and 1.40 A⁰.

Magnesium Oxide Electron Configurations

Electron configuration is the relative arrangement of the revolving electrons in different orbitals or shells. Let us explain it elaborately.

MgO has the electron configuration of magnesium and oxygen which are [Ne] 3s² and [Ne] 2s² 2p⁴. But when Mg becomes Mg²⁺ and O becomes O₂^2- then electron configuration will be [Ne] (for Mg²⁺) and [Ne] 2s² 2p⁶ (for O₂^2-).

Magnesium Oxide Oxidation State

MgO has an oxidation number of 0 because it is a neutral compound. In MgO, magnesium is in +2 and oxygen is in a -2 oxidation state which makes MgO a neutral chargeless compound.

Magnesium Oxide Acidity/Alkaline

MgO is a lewis base because it can donate its nonbonding electron pairs. When a metal reacts with oxide, a basic oxide is always formed. The pH value of MgO dissolved water is around 9.

Is magnesium Oxide odorless?

MgO has no characteristic odor. But breathing the fume of magnesium oxide can cause damage to the eyes and nose.

Is magnesium oxide paramagnetic?

Paramagnetic compounds are by the external magnetic field due to the presence of unpaired electrons. Let us check whether MgO is paramagnetic or not.

MgO is not a paramagnetic compound. All the electrons in Mg²⁺ are paired up ([Ne]). From the molecular orbital theory, it can be concluded that there are also no unpaired electrons in oxide ion (O₂^2-). Therefore, it is considered a diamagnetic compound.

Magnesium Oxide Hydrates

MgO crystal is hygroscopic because the crystals can absorb water molecules from the air atmosphere, but it is insoluble in water. When MgO comes to contact with water, it reacts, and a white powdered magnesium hydroxide is formed.

MgO (s) + H₂O (l) = Mg(OH)₂ (s).

Magnesium Oxide Crystal Structure

The crystal structure of the MgO is a halite-like cubic cell with space group Fm3̅m. In this crystal, each Mg²⁺ is attached to its six neighboring O^2- atoms to form MgO₆ octahedra and vice versa. All Mg-O bond length is 2.13 A⁰. The lattice parameters are a = b= c = 4.26 A⁰ and α = β = γ = 90⁰.

Magnesium Oxide Polarity and Conductivity

• MgO is neither a polar nor nonpolar compound. It is an ionic substance and the term “polar” only fits covalent molecules due to the electron displacement. In MgO, there is a distinct charge separation between electropositive magnesium and electronegative oxygen atoms.
• MgO shows a high thermal conductivity but low electrical conductivity. The thermal conductivity value of magnesium oxide is 30 W m^-1 K^-1.

Magnesium Oxide Reaction with Acid

MgO reacts with strong acids like hydrochloric acid (HCl) and nitric acid (HNO₃) and forms salt along with water.

• MgO (s) + HCl (aq) = MgCl₂ (aq) + H₂O (l)
• MgO (s) + HNO₃ (aq) = Mg(NO₃)₂ + H₂O (l)

Magnesium Oxide Reaction with Base

MgO does not react with the base because it is itself a lewis base. Neither it accepts H⁺ ions from the base nor it can donate electron pairs to the base.

Magnesium Oxide Reaction with Oxide

MgO reacts only with water (hydrogen oxide) and forms magnesium hydroxide.

MgO (aq) + H₂O (l) = Mg (OH)₂ (aq)

Conclusion

Magnesium oxide is a basic refractory metal, and it is stable at high temperatures. It has great use as an antacid to prevent stomach issues, heartburn, etc. It also generates magnesium in our blood.