Types of bonding

The different forms of bonding considered here are:

• metallic
• pure covalent
• polar covalent
• ionic

Metallic bonding

Metallic bonding is the type of bonding found in metallic elements. This is the electrostatic force of attraction between positively charged ions and delocalised outer electrons.

Pure covalent bonding

Atoms in a covalent bond are held together by electrostatic forces of attraction between positively charged nuclei and negatively charged shared electrons.

Electronegativity (see Patterns in the Periodic Table) is the measure the attraction of an atom involved in a bond has for the electrons of the bond.

When two atoms bonded by a covalent bond have the same electronegativity the electrons will be equally shared. This is called pure (non-polar) covalent bonding. For example, the chlorine molecule, Cl₂.

Polar covalent bonding

In most covalent compounds the bonding is polar covalent.

Covalent bonds with unequal electron sharing are called polar covalent bonds.

The atom with the higher electronegativity will have a greater share of the electrons. This will result in the atom having a slight negative charge compared to the other atom which will have a slight positive charge.

Ionic bonding

Ionic bonding is the electrostatic force of attraction between positively and negatively charged ions.

These ions have been produced as a result of a transfer of electrons between two atoms with a large difference in electronegativities.

Ionic bonding results from metals combining with non-metals. For example, sodium (a metal) combining with chlorine (a non-metal).

Difference in electronegativity of bonds