Is MgO an ionic or a covalent compound?

Magnesium oxide (MgO), often known as magnesia, is a metal oxide made up of magnesium (an alkaline earth metal) and oxygen.

Magnesium oxide is produced primarily by calcining naturally occurring minerals such as magnesite (MgCO3).

Seawater, subsurface brine deposits, and metamorphic rocks are all good places to look for it.

It’s a powdered white substance with no odour. It can collect moisture from the air since it is hygroscopic.

It has a high basicity because it forms basic magnesium hydroxide when it combines with water. It has a high melting point as well as a high boiling point.

Magnesium oxide (MgO) is a very valuable chemical. Because of its basic composition, it is frequently employed as an antacid. Magnesia is used to manufacture crucibles for the chemical industry. It’s also found in heating elements, fire-resistant materials, and other products.

So, is MgO an ionic or a covalent compound? Magnesium oxide (MgO) is an ionic chemical. The transfer of electrons from a metal (Mg) to a non-metal forms an ionic connection (O). To create Mg2+, Mg loses two valence electrons, which are acquired by O to form O2-. An ionic bond is established as a result of an electrostatic interaction between two oppositely charged ions.

Let’s take a closer look at this.

Why is MgO an ionic compound?

Magnesium is an alkaline earth metal with 12 protons and electrons in each atom.

Mg has a tendency to lose two valence electrons, resulting in an octet configuration similar to Neon. (The noble gas that is closest to you)

There are 10 electrons and 12 protons in the Mg2+ ion. Magnesium ions have a net positive charge because their protons outnumber their electrons.

Mg has the following electronic configuration: 1s22s22p63s2.

Mg2+ has the following electronic configuration: 1s22s22p6

2e Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ M

An O-atom is a non-metal with eight protons and eight electrons. Two electrons are required to complete the octet configuration, which is similar to Neon. Mg requires two valence electrons.

There are 10 electrons and 8 protons after obtaining two electrons. The ion has a net negative charge because the number of electrons is greater than the number of protons.

1s22s22p4 is the electronic configuration of O.

O2-‘s electronic arrangement is 1s22s22p6.

0 + 2e- 0+ 2e- 0+ 2e- 0+ 2e-

As a result, O took up the two electrons that Mg had lost. In this procedure, two ions with opposite charges are created.

These two ions are attracted to each other by an electric force, resulting in the development of a bond between them. Thus, an ionic bond is defined as a bond established by the transfer of electrons between a metal and a non-metal.

Factors Affecting a Compound’s Ionic Bonding

The three most important parameters that influence the degree of ionic bonding are:

  1. Ionisation Energy: In order to create a divalent cation, Mg loses two valence electrons.

The electromagnetic force attracts all electrons to the nucleus. Some energy is required to remove the electrons from the atom.

Ionization energy is the amount of energy necessary to remove an electron from an isolated gaseous atom in the ground state.

If the ionisation energy is higher, losing electrons is more difficult, and subsequent cation production is more difficult, and vice versa.

It’s a good thing because it gives you more energy.

  1. Electron affinity: A divalent anion is formed when an O-atom receives two electrons.

Gaining electrons releases energy because the addition of electrons exerts stress on other electrons, resulting in energy release.

When one electron is added to a neutral atom in its gaseous phase to generate a negative ion, the energy of the atom changes.

The easier it is to gather electrons and form an anion, the greater the magnitude of energy. Because energy is expelled, it is usually negative.

  1. Lattice Energy: Energy is released when cations and anions are brought near together.

Lattice energy is the amount of energy released when one mole of ionic solid is created from gaseous ionic components.

The magnitude of charges on cations and anions, as well as the distance between ions, play a role. The Born-Haber cycle can be used to investigate lattice energy.

The ease with which an ionic solid can be formed is determined by the magnitude of lattice energy. When the charges on atoms are large and the space between them is small, the lattice energy is high.

The ideal combination for forming an ionic bond is low ionisation energy, high electron affinity, and high lattice energy.

Ionic Characteristics in MgO as a Percentage

No ionic or covalent link is perfect. Every covalent bond has some ionic character, and every ionic bond has some covalent character.

Linus Pauling devised an empirical relationship to calculate the percentage ionic character in a bond.

It links ionic property to the electronegativity difference between two atoms.

Where the difference in electronegativity is denoted by.

Mg and O have electronegativities of 1.2 and 3.5, respectively, in MgO. is equal to 2.3.

Ionic character percentage= (1- e-(2.3/2)2) * 100= 73.35 percent

Fajan’s Law

Fajan’s rule postulates can be used to compare covalent character in ionic compounds and vice versa.

A compound with a small cation, large anion, and high cation charge is regarded more covalent, according to Fajan’s rule.

When the size and charge are the same, transition metals are said to have a higher covalent character than s block cations.

The charge density of a tiny cation is higher, making it easier to polarise the anion. The valence electrons are further away from the nucleus in a bigger anion, and the effective nuclear charge is lower, allowing it to be polarised more easily.

Higher anion polarizability and cation polarising power promote covalent character.

Example] CaO and MgO are both ionic compounds, although CaO has a higher ionic content than MgO.

This is due to Ca2bigger +’s size, which means it has less polarising power. CaO has a percentage ionic character of 79 percent.

Check out the article about CaO’s ionic nature.

Ionic and covalent bonding are compared.

The attraction force holds atoms and molecules together in a complex, stabilising the system by lowering its energy.

Chemical bonding is the term for this. There are two types of bonding.

Ionic Compound Covalent Compound
Complete transfer of electrons takes place for bond formation and both species achieve noble gas configuration.Electrons are shared between two atoms for bond formation and both species achieve noble gas configuration.
The electronegativity difference between atoms involved in bond formation is high.The electronegativity difference between atoms involved in bond formation is low.
A metal and a non-metal are involved in  bond formationNon-metal and non-metal/ metalloid are involved in bond formation
Bonds are very polar Bonds are relatively less polar or non-polar.
Ionic compounds are relatively stronger Covalent compounds are not as  strong as ionic compounds
Rules of maximum packing determine the geometry.Geometry can be found out using  VSEPR theory.
For example- MgO, NaCl, etc. For example- CH4, SiBr4, etc.

Ionic Compound Properties in General

• Physical properties– The electrostatic force attracts cations and anions to one other.

Ionic compounds are powerful due to the electrostatic force of attraction, and they are difficult to break. They are brittle because pressure causes them to split into small fragments.

• Melting and boiling points: Breaking the strong ionic connections between atoms requires a lot of energy.

As a result, ionic compounds have extremely high melting and boiling points.

• Polarity of ionic substances increases their solubility. Ionic chemicals are soluble in polar solvents according to the “like dissolves like” rule.

They are largely insoluble in non-polar solvents, as expected.

Ions can conduct electricity, but they can’t move in an ionic solid.

Ionic substances that are solid do not conduct electricity. They can conduct electricity if they are permitted to move freely, which is conceivable in either the molten or watery form of an ionic solid.

• Geometry and Shape– Because ionic bonds are non-directional, we can’t characterise the geometry and shape of the formula unit of ionic compounds.

The electrostatic force of attraction, which is non-directional in nature, attracts ions to one other.

• Lattice structure– An ionic compound can be thought of as a massive ion structure. An ionic lattice is a regular repeating structure that the ions have.

The structure is determined by the cation and anion sizes. Ionic solid MgO, for example, is found in a cubic crystal structure.


The complete transfer of two electrons from the valence shell of Magnesium metal to the outermost shell of the O- atom forms MgO, an ionic compound.

• The electrostatic forces of attraction between the magnesium cation and the oxygen anion form an ionic connection.

• In MgO, the percentage of ionic character is 73.35 percent.

• Magnesium oxide (MgO) is a versatile chemical that can be used in a variety of industries.

Read more: Molecular Geometry, Hybridization, and Polarity of ClF3 Lewis Structure

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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