Covalent Bond



What is Covalent Bond?

Covalent bond is formed when a pair of valence electrons are mutually shared between the atoms of the element and the stable attractive and repulsive forces existing between these atoms is known as covalent bonding. Here the valence electrons are not transferred between the atoms but are equally shared by both the atoms. Covalent bond is formed only by donating the electrons by each of the participating atoms of the element.

Mutual sharing of pair of valence electrons between the atoms leads to the formation of covalent bond

The covalent bonds are classified into three types based on the number of pair of valence electrons shared by the atoms of the element.

  • Single Covalent Bond - It is formed when only one pair of electrons are shared between the atoms of the element, example - HCl, H2.
  • Double Covalent Bond - It is formed when two pairs of electrons are shared between the atoms of the element, example - O2.
  • Triple Covalent Bond - It is formed when three pairs of electrons are shared between the atoms of the element, example - N2.

Example

Let us consider a molecule of HCl as an example of covalent bond formation. The covalent bond formation in HCl (Hydrogen Chloride) can be understood by Lewis electron-dot structure.

Lewis Electron-dot Structure of HCl

Lewis electron dot structure is based on the concept of number of valence electrons present in the outermost shell of the atom.

The element HCl contains two atoms H and Cl.

H (Hydrogen) Atom

The electronic configuration of H is - 1S1

By the above electronic configuration, we can observe that only one valence electron is present in the Hydrogen atom. So the electron dot structure of H atom can be written as

Na-dot structure

Cl (Chlorine) Atom

The electronic configuration of Cl is - 1S2 2S2 2P6 3S2 3P5

By the above electronic configuration, we can observe that 7 valence electrons are present in the outermost shell of Cl atom. So the electron dot structure of Cl atom can be written as

Na-dot structure

Single Covalent Bond Formation in HCl

The valence electron of H (Hydrogen) atom is shared with the valence electron of Cl (Chlorine) atom to attain stable electronic configuration (Octet configuration). Therefore a single covalent bond is formed between Hydrogen and Chlorine atoms.

Na-dot structure

Characteristics of Covalent Solids

The covalent solids possess the following characteristics...

  • Covalent solids are very hard and brittle.
  • Covalent solids have low melting and boiling points.
  • Bonds are directional in covalent solids.
  • Covalent solids possess high thermal and electrical conductivities due to presence of free electrons.
  • Covalent solids are soluble in non-polar solvents like ether.