What is polarity ?
What are polar and non polar substances ?
In homo-atomic molecules having the same type of atoms are present .In them sharing of electrons occur the shared pair remain in the middle that is equal attraction by atoms towards shared pair.
The hetero-atomic molecules (having different types of atoms in them) when sharing of electrons occur the shared pair do not lie in middle, it gets displaced towards more electronegative atom.
So, it will acquire a partial negative charge and other atoms will acquire partial positive charge. Due to this, the poles are developed and the bond formed is a polar covalent bond.
Non-Polar Covalent bonds:
If two similar atoms come close to each other and form a bond by sharing their electrons, Hence no poles are developed. This leads to the formation of completely non-polar bonds.
If two hydrogen atoms form a bond, the electron pair will lie exactly in the middle between
the two atoms.
The electron cloud is completely symmetrical and there is no charge separation at all.
For Ex: Cl2,F2,N2etc.
Polar covalent bonds
When two dissimilar atoms, have different electronegativities combined together to form a covalent bond, the shared pair of electrons does not lie at an equal distance from the nuclei of both the bonded atom but shifts towards the atom having greater electronegativity.
The more electronegative atom attracts the electrons more strongly, the distribution of
electrons get distorted i.e. the electron cloud is displaced more towards the more
electronegative atom.
One end of the molecule, having more electronegative atom becomes slightly negatively
charged while the other end acquire slightly positive charge.
Positive and negative poles are developed and this type of bond is called polar covalent
bond.
For Ex: