Is Magnesium oxide (MgO) ionic or covalent? Types of bond in MgO

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Is MgO ionic or covalent?

Magnesium oxide is found in nature as the mineral periclase. It appears as a white powder and is generally odorless in nature. It is an inorganic compound and has a MgO chemical formula. It is soluble in acid, ammonia, water but insoluble in alcohol.

In this article, we will discuss Is Magnesium oxide (MgO) is ionic or covalent? Formation of bond in MgO, etc.

So, Is MgO ionic or covalent? MgO is an ionic compound and consists of Mg2+ and O2- ions which are held together by ionic bonding. The bond formed between the metal (magnesium) and nonmetal (oxygen) is ionic due to the large gap of electronegativity difference exists between them.

Name of MoleculeMagnesium Oxide
Chemical formulaMgO
Molar mass40.304 g/mol
Bond typeIonic
NatureBasic

Why Magnesium oxide (MgO) is an ionic compound?

An ionic compound is a compound that is formed when the atoms lose or gain valence electrons to become more stable and form positive and negative ions.

Further, these charged ions are held by the electrostatic force of attraction, and eventually, a bond is formed between them which is called an ionic bond.

Usually, the metal atom transfers the electron whereas the nonmetal accepts the electron.

Here, in the case of the MgO compound, magnesium is a metal atom that belongs to the alkali group and oxygen is a nonmetal that belongs to the p-block group.

So, magnesium metal transfers its electrons whereas oxygen atom will accept it and a bond will form between them which is called an ionic bond.

Ionic bond formation in MgO (magnesium oxide)

As we see in the above figure, the magnesium metal is transferring its electrons and oxygen as a nonmetal accepting the electrons, and both these formed Mg2+ and O2– ions which are held together by the electrostatic force of attraction, and an ionic bond forms between them.

Examples of some more ionic compounds – MgCl2, Na2O, NaCl, etc.

Also Read:

How ionic bond is formed in MgO?

An ionic bond is formed either by giving or taking electrons.

The formation of ionic bond in MgO usually take three process-

(1). Formation of cation(Mg2+)

A cation is formed when the metal atom loses its electron to obtains stability. In the case of MgO, the magnesium atom is a metal that belongs to group 2 in the periodic table and has an atomic number of 12.

The electronic configuration for magnesium is 1s22s22p63sor [2, 8, 2]. So, by losing 2 electrons, the magnesium metal electronic configuration will be [2, 8]. So, now it has an electronic configuration close to the noble gas configuration and has 8 electrons in the outermost shell.

Hence, the magnesium wants to lose 2 electrons from its outermost shell to achieve stability. 

formation of cation in MgO ionic compound

(2). Formation of the anion(O2-)

An anion is formed when the nonmetal gains the electrons to obtains stability. In the case of the MgO compound, oxygen is a nonmetal that belongs to group 16 in the periodic table and has an atomic number of 8.

The electronic configuration for oxygen is 1s22s22p4 or [2, 6]. So, by gaining 2 electrons, the oxygen nonmetal electronic configuration will be [2, 8]. So, now it has an electronic configuration close to the noble gas configuration and has 8 electrons in its outermost shell.

Hence, the oxygen nonmetal gains the 2 electrons to achieve the stable form.

formation of anion in MgO ionic compound

(3). Electrostatic force attraction between ions(Mg2+ and O2-)

Electrostatic force is non-contact force that attract the positive and negative charged particles or objects without touching them.

We know that opposite charges will always attract each other. So, the formation of ions Mg2+ and O2- will attract each other because of positive and negative charges.

Therefore, both these ions are linked together by the electrostatic force of attraction and a formation of a bond occurs between them which is called an ionic bond or electrovalent bond.

Ionic bonding in MgO (magnesium oxide)

Why is MgO not a covalent compound?

covalent bond is formed when sharing of electrons is done between the atoms to achieve stability. 

Usually, covalent bonds formed between the two nonmetals, between p-block and p-block, and formed when electronegativity difference between atoms exist less than 2.

Examples of some compounds that form covalent bonds – H2O, NH3, H2S, SO2, NO2, AlCl3, etc.

Also Read:

According to the Pauling scale of electronegativity-

  • The covalent bond is formed between the two atoms when their electronegativity difference occurs less than 1.7.
  • The ionic bond is formed between the two atoms when their electronegativity difference occurs more than 1.7.

pauling scale for chemical bonds

Now check the electronegativity difference in MgO compound-

⇒ The electronegativity value for magnesium atom = 1.31

⇒ The electronegativity value for oxygen atom = 3.44

∴ The difference of the electronegativity between magnesium and oxygen atoms = 2.13

So, the difference in electronegativity between magnesium and oxygen is more than 1.7, hence, it is large enough to make an ionic bond between them as per the Pauling scale of electronegativity.

Also, in the MgO compound, there is no sharing of electrons involves, magnesium metal atom transfer its electrons and oxygen as nonmetal accept the electron to achieve stability by completing the octet.

And a bond is formed between the ions which is called an ionic bond.

Is MgO covalent or ionic in nature?

Energy involving in the process of ionic bond formation in MgO?

When a chemical bond is formed it releases energy, which helps to attain stability between the new bonds.

The formation of a bond releases the energy whereas the breaking of the bond absorbs the energy.

There are three types of energy involved in the process of ionic bond formation in MgO.

(a). Ionization enthalpy

(b). Electron gain enthalpy

(c). Lattice energy

⇒ Ionization enthalpy

Ionization enthalpy is the amount of energy required to remove the loose electron of an isolated gaseous atom from its outermost shell, then convert it into a gaseous positive ion.

Ionization enthalpy is always positive and occurs when an electron loses from the atom.

So, in the case of ionic bond formation in MgO, when an electron is loosed or released from the magnesium metal then the energy associated with it is ionization enthalpy.

energy required during the process of cation formation in MgO

⇒ Electron gain enthalpy

This energy is just opposite to ionization energy. The electron gain enthalpy is the enthalpy that occurs when an electron is added to an isolated atom in the gaseous phase, then convert this isolated atom into a gaseous negative ion.

The electron gain enthalpy may be positive or negative but most of the time it is negative. 

So, in the case of ionic bond formation in MgO, when an electron is accepted or is added to the oxygen atom then energy associated with it is electron gain enthalpy.

energy required during the process of anion formation in MgO

 

⇒ Lattice energy

The lattice energy is the energy that releases when 1 mole of an ionic bond is formed from adding gaseous anion and cation.

The more the lattice energy releases during the formation of an ionic bond, the higher is the stability of that bond.

So, in the case of ionic bond formation in MgO, when cation(Mg2+) is attracted by anion(O2-), then some amount of energy is released which is called lattice energy.

energy releases during the process of ionic bond formation in MgO

As you see in the above figure when 1 mole of cation(Mg2+) diffuses with one mole of the anion(O2-) then one mole of solid(MgO) is formed.

And the energy released during the formation of ionic bonds in MgO is lattice energy.

Properties of Magnesium oxide

  • MgO consists of a lattice of Mg2+ ions and O2− ions held together by ionic bonding.
  • It has a boiling point of 3,600 °C and a melting point of 2,852 °C.
  • It is soluble in water, ammonia, acid but insoluble in alcohol.
  • It has a dipole moment of 6.2 ± 0.6 D.
  • Magnesium oxide has an octahedral coordination geometry for Mg2+ and O2-.
  • It combines quickly with water to form magnesium hydroxide.
  • It is physically and chemically stable at high temperatures.
  • The net charge in magnesium oxide is zero.

Uses of Magnesium oxide

  1. It is used in refractory material because of its stability at high temperatures.
  2. It is used as a protective coating in plasma displays.
  3. It is used as an anticaking agent.
  4. It is used as an antacid in medical for the relief of heartburn and also used in conditions of indigestion.
  5. MgO is used as fireproofing in construction material because of its unique characteristics like moisture resistance, fire resistance, etc.
  6. It is used in wastewater treatment, air emission treatment, and in waste management industries.
  7. It is used as an electrical insulator in tubular construction heating elements.
  8. Magnesium oxide is used as an insulator in heat-resistant electrical cables.

FAQ

Which has a more covalent character between MgO and CaO?

First of all, both MgO and CaO are ionic in nature because of the existence of a large electronegativity difference in value between the atoms of these compounds.

But no compound in the universe exists as 100% ionic. Therefore, MgO and CaO have some covalent characters even they are ionic in nature.

So, which has a more covalent character? MgO has a more covalent character than CaO, this is because Mg2+ has greater polarizing power than Ca2+, Hence, Mg2+ drawback the bonding electrons from O2- to a greater extent than Ca2+ corresponding its high covalent character.

Which has more covalent character MgO or BeO?

Both beryllium and magnesium belong to that same group and have the same valency with the same charge. But beryllium is present just above the magnesium.

As we go down the periodic group, the atom size increases. Hence, the magnesium is larger than beryllium.

Going by the trick to finding more covalent characters, use the C/S ratio formula.

⇒ C = Charge of cation

⇒ S = Size of the atom

“Larger is the C/S ratio, more will be the covalent character”.

So, both beryllium and magnesium have the same charge but the atomic size of magnesium is larger than beryllium.

Therefore, the C/S ratio of BeO is larger than the C/S ratio of magnesium.

∴ The BeO has a more covalent character than MgO.

Summary

  • Is Magnesium oxide (MgO) ionic or covalent? MgO is an ionic compound because the bond formed between magnesium and the oxygen atom is ionic in nature, it is formed as magnesium atom loses two electrons to form Mg2+ ion and oxygen atom accepts these electrons to form O2 ion, later these ions(Mg2+ and O2-) are attracted by the electrostatic force of attraction and form the ionic bond.
  • MgO is ionic in nature but still, it has a covalent character also or you can say MgO is not 100% ionic in nature.
  • The difference in electronegativity between magnesium(1.31) and oxygen(3.44) is 3.44–1.31=2.13 which is higher than 1.7, hence, according to the Pauling scale, the bond formed between magnesium and an oxygen atom is ionic in nature.
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