What do you understand by bond pairs and lone pairs of electrons? Illustrate by giving one example of each type.

In the context of chemistry, bond pairs and lone pairs of electrons are terms used to describe the arrangement of electrons around an atom in a molecule. These terms are often associated with the VSEPR (Valence Shell Electron Pair Repulsion) theory, which explains the three-dimensional geometry of molecules based on the repulsion between electron pairs.

Bond Pair: A bond pair of electrons is a pair of electrons that are shared between two atoms, forming a covalent bond. Covalent bonds are formed when atoms share electrons to achieve a more stable electron configuration. The electrons involved in a bond pair are positioned in the space between the two atoms involved in the bond.

Example: In a molecule of water (H₂O), each hydrogen atom shares a pair of electrons with the oxygen atom. This forms two bond pairs of electrons in the molecule. The Lewis structure representation of water is: H-O-H, where "-" represents a covalent bond.

Lone Pair: A lone pair of electrons refers to a pair of electrons that are not involved in forming a bond but are located on an atom's outer shell. Lone pairs are typically represented as dots around the atom's symbol in Lewis structures. They have a significant influence on the molecule's shape due to their tendency to repel other electron pairs.

Example: In the ammonia molecule (NH₃), the nitrogen atom has three bond pairs (forming bonds with three hydrogen atoms) and one lone pair of electrons. The lone pair pushes the bonding electron pairs away, resulting in a trigonal pyramidal molecular geometry. The Lewis structure representation of ammonia is: H-N-H, with a lone pair of electrons represented as a pair of dots on the nitrogen atom.

In summary, bond pairs are electron pairs shared between atoms to form covalent bonds, while lone pairs are electron pairs not involved in bonding and can affect the molecule's geometry due to electron repulsion.