Bond pair of electrons:
A bond pair is a pair of electrons that is shared between two atoms to form a covalent bond. These electrons participate directly in bond formation and hold the atoms together.
Example:
In a hydrogen molecule:
H — H
The single bond between the two hydrogen atoms consists of one bond pair of electrons.
Lone pair of electrons:
A lone pair is a pair of electrons that is not shared with another atom and remains localized on a single atom. These electrons do not participate in bond formation but influence the shape and properties of molecules.
Example:
In a water molecule (H2O), the oxygen atom has two lone pairs of electrons:
H — O — H
The non-bonding electron pairs on the oxygen atom are lone pairs.
Conclusion:
Bond pairs are responsible for forming covalent bonds between atoms, while lone pairs remain unshared and affect molecular geometry and reactivity.
The correct increasing order for bond angles among \( \text{BF}_3, \, \text{PF}_3, \, \text{and} \, \text{CF}_3 \) is: