Polar covalent bonds
It is unusual for pure covalent bonds to exist between atoms of different elements. Usually, one of the atoms involved in the covalent bond will be more electronegative and will have a greater attraction for the bonding pair of electrons. This gives rise to polar covalent bonding.
A polar covalent bond is a bond formed when a shared pair of electrons are not shared equally. This is due to one of the elements having a higher electronegativity than the other.
The shared pair of electrons between an atom of hydrogen and an atom of bromine are not shared equally. Since bromine has a greater electronegativity than hydrogen, it will pull the bonding electrons towards itself.
This makes bromine slightly negative (\(\delta-\)) and hydrogen slightly positive (\(\delta+\)). This is known as a dipole.
The shaded area shows where the bonding electrons are likely to be found.
