Chemical bonding – Covalent

Chemical bonding occurs when atoms combined together. There are some atoms that don’t undergoes chemical bonding examples are the noble gas found in the group 8 of the periodic table

Now the question is, why does some atoms undergoes chemical combination and while others don’t?

The reason is because the atoms of those element that does not undergo combination already have completely filled outermost shell and they are thereby stable.

While other atoms that undergoes combination have incomplete electron in their outermost shell which gives them the tendency to combine with other atoms in other to be complete their shells.

Noble gases have stable atom, a stable atom is a nonreactive atom, and is unlikely to bond with other atoms. This is why the noble gases are nonreactive and why they don’t exist as molecules rather they exist as atoms.

There are different types of chemical bonding, but before we proceed, let us quickly look at the terms involved in bonding


Bonding terms

Bond length: this is the distance between the nuclei of the atoms when they combines.

Bond energy: this is the amount of energy that must be added to the system to break the bonds that have formed.

Bond strength: means how strongly one atom attracts and is held to another

The relationship of a bond length, size and number of bonds to the atom is in as follows.

The shorter the bond length, the stronger the bond between the atoms, and the smaller the atoms involved, the stronger the bond.

The greater the number of bonds between atoms, the greater will be the bond strength.


Types of bonding

  • Covalent bonding
  • Ionic bonding
  • Dative bonding
  • Metallic bonding

Covalent bonding is a type of bonding that involves sharing of electron between two atoms. It occurs between two non-metal atoms. Eg O2 H2 cl2

However when these two atoms are sharing electrons, it can either be evenly shared among the atoms or unevenly shared due to difference in electronegativity which leads to polar and non-polar molecules.

Check on the tutorial section to read more on polar and non polar molecules

Example of covalent bonding

Hydrogen and chlorine combines to form hydrogen chloride

First lets write out the electronic configuration of theses two atoms

H =  1s1

Cl =  1s2 2s2 2p6 3s2 3p5

From their configuration? Hydrogen has 1 electron in the outermost shell and it requires one more electron for it to be stable.

 While on the other hand, chlorine has 7 electrons in its outermost shell and also needed one electron to be stable.

Also, remember that these electrons are always in pairs. Check Aufbau’s principles for more on that.

So, when you pair the electrons in chlorine you will have 1 unpaired electron which will then combined with unpaired electron of hydrogen.


Covalent bonding in a molecule of hydrogen chloride


Example 2

Combination of Nitrogen with Hydrogen to form Ammonia

N =7 and has 3 unpaired electrons

H=1 and has 1 unpaired electrons

So, three of hydrogen atoms will combine with nitrogen atom.


Covalent bonding in a molecule of ammonia


Check the tutorial section for the continuation on the other types of chemical bonding.



Draw simple diagrams to show how electrons are arranged in the following covalent molecules:

(a) Calcium oxide (CaO)

(b) Water (H2O)

(c) Chlorine (Cl2)







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