Is Magnesium oxide (MgO) ionic or covalent? Types of bond in MgO
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, and water but insoluble in alcohol.
In this article, we will discuss Is Magnesium oxide (MgO) ionic or covalent? Formation of bond in MgO, etc.
Is MgO ionic or covalent?
Magnesium oxide, MgO, is considered an ionic compound. It contains two atoms, Magnesium (Mg) which is metal, and Oxygen (O) which is a nonmetal, both these are linked together by ionic bonding.
Also, the bond formed between magnesium (Mg) and oxygen (O) is ionic due to the large gap of electronegativity difference that exists between them.
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.
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.
It is formed as the magnesium atom loses two electrons to form an Mg2+ ion and the oxygen atom accepts these electrons to form an O2– ion, later these ions(Mg2+ and O2-) are attracted by the electrostatic force of attraction and form the ionic bond 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 obtain 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 1s22s22p63s2 or [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.
(2). Formation of the anion(O2-)
An anion is formed when the nonmetal gains the electrons to obtain 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.
(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.
Why is MgO not a covalent compound?
A covalent bond is formed when sharing of electrons is done between the atoms to achieve stability.
Usually, covalent bonds are formed between the two nonmetals, between p-block and p-block, and formed when the electronegativity difference between atoms exists less than 2.
Examples of some compounds that form covalent bonds – are H2O, NH3, H2S, SO2, NO2, AlCl3, etc.
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.
Now check the electronegativity difference in the MgO compound-
⇒ The electronegativity value for magnesium atom = 1.31
⇒ The electronegativity value for oxygen atom = 3.44
∴ The difference in 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 involved, magnesium metal atom transfers its electrons and oxygen as nonmetal accepts the electron to achieve stability by completing the octet.
And a bond is formed between the ions which are called an ionic bond.
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.
⇒ Electron gain enthalpy
This energy is just the opposite of 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.
⇒ Lattice energy
The lattice energy is the energy that releases when 1 mole of an ionic bond is formed by adding gaseous anion and cation.
The more the lattice energy releases during the formation of an ionic bond, the higher 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.
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.
It has a boiling point of 3,600 °C and a melting point of 2,852 °C.
It is soluble in water, ammonia, and 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
It is used in refractory material because of its stability at high temperatures.
It is used as a protective coating in plasma displays.
It is used as an anticaking agent.
It is used as an antacid in medicine for the relief of heartburn and also used in conditions of indigestion.
MgO is used as fireproofing in construction material because of its unique characteristics like moisture resistance, fire resistance, etc.
It is used in wastewater treatment, air emission treatment, and in waste management industries.
It is used as an electrical insulator in tubular construction heating elements.
Magnesium oxide is used as an insulator in heat-resistant electrical cables.
FAQ
Is MgO Covalent or Ionic?
MgO is an Ionic compound, not a covalent. Since the gap of electronegativity value between magnesium (1.31) and oxygen (3.44) is large, therefore, the bond formed in Magnesium oxide (MgO) is Ionic.
It consists, of two ions, Mg2+ and O2-, both of these are held together by ionic bonding.
Why MgO is Ionic and not a covalent?
The first reason is, that magnesium is a metal, and oxygen is nonmetal, hence, transferring of electrons will take place between them, which will cause ionic bond formation in MgO.
There is a large gap of electronegativity between the magnesium and oxygen, more than 1.7, hence, as per the Pauling scale, the ionic bond will form in magnesium oxide.
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 though they are ionic in nature.
So, which has a more covalent character, MgO or CaO? MgO has a more covalent character than CaO, this is because Mg2+ has greater polarizing power than Ca2+, Hence, Mg2+ drawbacks the bonding electrons from O2- to a greater extent than Ca2+ corresponding to 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 (Mg) and the oxygen (O) atom is ionic in nature. It is formed as the magnesium atom loses two electrons to form an Mg2+ ion and the 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 in MgO compound.
The difference in electronegativity between magnesium (Mg) and oxygen (O) is 3.44–1.31=2.13 which is higher than 1.7, hence, according to the Pauling scale, the bond formed between magnesium (Mg) and oxygen (O) atom is ionic in nature.
MgO is ionic in nature but still, it has a covalent character also or you can say MgO is not 100% ionic in nature.
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
Topblogtenz is a website dedicated to providing informative and engaging content related to the field of chemistry and science. We aim to make complex subjects, like chemistry, approachable and enjoyable for everyone.
