Explain the concept of polar and non-polar covalent bonds.

Polar covalent bonds have an unequal distribution of electron density, while non-polar covalent bonds have equal distribution.

Covalent bonds are formed when two atoms share a pair of electrons. The type of covalent bond that forms, whether polar or non-polar, depends on the electronegativity of the atoms involved. Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.

In a polar covalent bond, the electrons are not shared equally because one atom has a stronger electronegativity than the other. This results in a bond where the electron pair is displaced towards the more electronegative atom. This atom then gains a partial negative charge, while the less electronegative atom has a partial positive charge. The difference in electronegativity values between the two atoms determines the polarity of the bond. The greater the difference, the more polar the bond. Examples of polar covalent bonds include the bonds in water (H2O) and hydrogen fluoride (HF).

On the other hand, a non-polar covalent bond is one where the electrons are shared equally between two atoms. This happens when the atoms involved have the same or similar electronegativity values. The electron pair is equally attracted to both atoms, resulting in a balanced distribution of electron density. This means there is no charge separation, and the molecule is overall electrically neutral. Examples of non-polar covalent bonds include the bonds in oxygen (O2) and methane (CH4).

In summary, the key difference between polar and non-polar covalent bonds lies in the distribution of electron density. Polar covalent bonds have an unequal distribution due to differences in electronegativity, leading to partial charges. Non-polar covalent bonds, however, have an equal distribution of electron density, resulting in no charge separation. Understanding these concepts is crucial in predicting the properties and behaviours of different molecules.