Final answer:
The main difference between polar and nonpolar covalent bonds is the equality of electron sharing; nonpolar bonds share electrons equally, while polar bonds do not, leading to a charge imbalance and a dipole moment.
Step-by-step explanation:
The difference between polar and nonpolar covalent bonds is based on how the electrons are shared between the atoms involved in the bond. In a nonpolar covalent bond, the electrons are shared equally between the two atoms, leading to a balanced distribution of electrical charge. Examples of nonpolar covalent bonds include the bonds between two hydrogen atoms or between two carbon atoms.
On the other hand, a polar covalent bond occurs when one atom has a greater attraction for the bonding electrons than the other atom, resulting in an unequal sharing of electrons. This causes one end of the bond to be slightly positive (δ+) and the other to be slightly negative (δ-), generating a dipole moment. Water is a classic example of a molecule with polar covalent bonds, where the oxygen atom has a greater electronegativity than the hydrogen atoms.
The distinction between polar and nonpolar covalent bonds can also be understood in terms of electronegativity difference. If the difference in electronegativity between the bonded atoms is less than 0.5, the bond is generally considered nonpolar covalent. If the difference is between 0.5 to 1.9, the bond is polar covalent. However, if the difference is greater than 1.9, the bond tends to be ionic rather than covalent.