Is CaO an ionic or a covalent compound?

Calcium is a member of the alkali earth metals family, which is found in the second group of the periodic table. Calcium creates a number of important chemicals, one of which is calcium oxide (CaO).

Calcium oxide, sometimes known as “quicklime” or “burnt lime,” is a white crystalline substance that is commonly utilised chemically. It is thought to be one of the world’s oldest compounds.

Calcium oxide chemistry is quite fascinating. Calcium oxide, on the other hand, frequently confounds individuals with its qualities and nature. The type of chemical bonding is one such factor.

Is calcium oxide covalent or ionic? Calcium oxide is an ionic compound because it contains a metal (calcium) and a nonmetal (oxygen) (oxygen). Second, the calcium atom easily loses two of its outermost shell electrons because to the substantial disparity in electronegativities (E=2.4), which are gained by the oxygen atom. Calcium oxide (CaO) is ionic because it is formed by the loss of electrons by one atom and the acquisition of electrons by another.

Chemical Bonds: What Are They and How Do They Work?

When we look at the periodic table as a whole, we can see that there are three categories of elements. Metals, nonmetals, and metalloids are the three types.

Every element seeks stability, which it achieves by bonding. A chemical connection is established between components depending on the sorts of elements involved. (There are occasional exceptions to this rule, such as when the electronegativities of elements are almost identical.)

A covalent bond is produced when a metal interacts with another metal, a nonmetal connects with another nonmetal, or a metalloid interacts with a nonmetal.

When a metal interacts with a nonmetal, however, an ionic bond is generated between the two.

Recognize the type of components interacting to identify the following compounds based on the chemical bond present between them (exceptions not included):

H2O? It has a covalent bond.

NH3? It has a covalent bond.

MgCl2? It’s an ionic substance.

NaCl? It’s an ionic substance.

HCl? It has a covalent bond.

SiO2? It has a covalent bond (as silicon is a metalloid)

What is the definition of an ionic bond?

When two elements interact and one loses electrons while the other gains the same electron, the bond produced is called an ionic bond.

The significant disparity in electronegativities of the two elements causes this loss and gain of electrons. As a result, an element with a greater electronegativity can draw electrons from a lower electronegativity element.

A “donor” is an element that is losing electrons, whereas a “acceptor” is an element that is acquiring electrons and has a higher electron affinity.

The difference between the electronegativities (E) of the donor and acceptor should be larger than or equal to 2.0 for a compound to be ionic.

Because the difference in electronegativities between metals (which are on the left side of the periodic table) and nonmetals (which are on the right side of the periodic table) is usually greater than 2.0.

As a result, they tend to create ionic bonds in which the metal functions as the donor and the nonmetal acts as the acceptor. NaCl, MgCl2, AlCl3, and CaO are examples of this ionic interaction.

What is the definition of a covalent bond?

Covalent bonds, unlike ionic bonds, are created by the “sharing” of electrons between two elements. There are no electron losses or gains.

The electrons in an atom’s outermost shell are usually the shared pair of electrons. These are referred to as “bonded pairs of electrons” because they establish covalent bonds between atoms of two different elements.

Because of minor changes in electronegativities, electrons are shared between elements. As a result, neither of them is powerful enough to attract the shared electrons to themselves. As a result, they decide to share electrons with one another.

The difference between the electronegativities (E) of the donor and acceptor should be less than 2.0 for a compound to be covalent. A pure covalent bond is established when the difference is less than 1.7.

If the electronegativities of the two elements differ by 1.7 to 2.0, the bond produced is still covalent, but it is “polar covalent,” because one element is somewhat stronger than the other.

Because the difference in electronegativities between two metals, two nonmetals, or a metalloid and a nonmetal is less than 2.0, they tend to form covalent bonds.

CO2, SiO2, NO2, CCl4, and H2O are examples of covalent interactions.

Do you have any idea? Because of ionic and covalent bondings, there are significant variances in physical and chemical properties. Ionic compounds, for example, have much higher melting and boiling temperatures than covalent molecules.

Due to the existence of free ions, ionic compounds can conduct electricity when dissolved in water, whereas covalent compounds cannot.

Calcium Oxide is a type of calcium oxide.

At room temperature, calcium oxide, popularly known as “lime,” “quicklime,” or “burnt lime,” is a white, alkaline, crystalline substance. It can also be found in the form of granular powder or gray-white lumps at different temperatures.

Calcium oxide has a very high melting point of 2572°C, making it a particularly stable chemical. Because it creates calcium hydroxide when it reacts with water, it is insoluble in water. It can be dissolved in acids.

Since the Middle Ages, it has been one of the most frequently and commonly used compounds. It is created naturally in nature when calcium carbonate (CaCO3)-containing minerals, such as seashells and limestones, decompose.

Calcium oxide is produced during the breakdown reaction, as well as carbon dioxide gas.

CaCO3 → CaO + CO2

Do you have any idea? The creation of calcium oxide is thought to be the first chemical reaction ever discovered by humans. Its traces can be traced all the way back to the Stone Age.

Calcium Oxide Ionic Bonding

One atom of calcium (with two electrons in the outermost shell) and one atom of oxygen make up the calcium oxide (CaO) molecule (with six electrons in the outermost shell).

The ground state electron configurations of calcium and oxygen are shown here.

1s2, 2s2 2p6, 3s2 3p6, 4s2 (atomic number = 20)

1s2, 2s2, 2p4 (atomic number = 8)

The electronegativities of calcium and oxygen are vastly different: E (Ca) = 1.0 and E (O) = 3.5. E = 3.5 – 1.0 = 2.5 is the difference.

When the difference between calcium and oxygen is larger than 2.0, ionic bonds are formed, in which calcium loses two electrons from its outermost shell and oxygen gets two electrons.

Calcium becomes a cation (Ca2+) after losing two electrons, and oxygen becomes an anion after obtaining two electrons (O2-). In an ionic state, the electronic configurations of calcium and oxygen are as follows:

1s2, 2s2 2p6, 3s2 3p6 Ca2+ (atomic number 20)

1s2, 2s2, 2p6 O2- (atomic number 8)

Both atoms have achieved stability by completing 8 electrons in their outermost shells and attaining the nearest noble gas form, as seen here.

Calcium accomplished this by losing two electrons, whereas oxygen did so by obtaining two electrons. This is how an ionic link between them is established.

Do you have any idea? Because most of calcium oxide’s reactions are highly violent, it should be handled with caution. Calcium oxide can irritate your eyes and skin, and inhalation of the substance might induce sneezing and coughing.

Calcium Oxide’s Applications

Calcium oxide is used in a variety of applications, including:

It’s used to make cement, paper, and high-grade steel and iron, among other things.

It is employed in many acid-base reactions, such as the production of caustic soda, due to its alkaline nature (NaOH)

Insecticides and pesticides contain it.

It’s also employed in medical settings.

It is used as a reagent in laboratories for precipitation and dehydration reactions.

It is used as a food additive because it is alkaline and acts as an acidity regulator.

Soil acidity is reduced, and soil quality and fertility are improved.

Do you have any idea? Calcium oxide is thrown into lakes that have grown acidic due to nitric and sulfuric acid in rains. It neutralises these acids due to its alkaline composition.


We studied about the many sorts of components and the different types of connections that result from their interaction in this post.

We looked at how ionic and covalent connections are created, as well as how electronegativity influences the type of bonding. Ionic bonds have electronegativity differences greater than 2.0, while covalent bonds have electronegativity differences less than 2.0.

We also looked into the ionic bonding in CaO and its applications in numerous domains.

Good luck with your studies!

Read more: MO Diagram, Molecular Geometry, Hybridization, and Lewis Structure of HNO3

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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