CBSE Class 10 Answered

A polar bond results when different atoms share electrons. One atom will attract the bonding electrons more strongly than the other atom and will acquire more than a half share of these electrons. This leaves the other atom with less than a half share and makes the electron distribution unsymmetrical. On a time-average basis the electrons spending more time with one atom and cause it to have a partial negative charge. The other atom, deficient in electrons, acquires a partial positive charge. A polar bond is a type of covalent bond between two atoms or more in which electrons are shared unequally. For example: H₂O; here hydrogen has a slight positive charge and oxygen has a slight negative charge. 

Polar covalent bond results with an unequal sharing of electrons. It's a molecule in which the bond dipoles present do not cancel each other out and thus results in a molecular dipole.