Covalent Bond?

Question

Please explain me what is polar and non-polar covalent bond.

Answer 1

All covalent bonds involve the sharing of electrons between atoms. What can differ is whether the electrons in the bond are shared equally or unequally between the atoms in the bond.

In a nonpolar covalent bond, the electrons are shared equally.

In a polar covalent bond, the electrons are shared unequally, tending to spend more time around one of the atoms in the bond. Because electrons have a negative charge, the atom that the bonding electrons spend more time around becomes slightly negatively charged. The atom that gets less attention from the bonding electrons becomes slightly positively charged. The existence of these small partial charges on the atoms involved in this type of covalent bond is what makes the bond "polar".

What determines whether a covalent bond will be polar or nonpolar? The electronegativaties of the atoms involved in the covalent bond. Think of electronegativity as a measure of how much bonding electrons "like" to hang around an atom. If two atoms in a bond have identical (or nearly identical) electronegativity values, the bonding electrons split their time equally between the two atoms and the bond is NONPOLAR. If the electronegativity values are different, then the electron sharing becomes lopsided and you get a polar covalent bond.

Answer 2

A polar covalent bond shares the pair of electrons unequally between the two atoms, as in Cl-H. The H has electronegativity 2.2, while C is 3.0. So the H is a little bit (+), while the Cl is a little bit (-). By contrast, in H-H and Cl-Cl, the electronegativities of the bonded atoms are the same, so the bond is nonpolar covalent.