Question
What do you understand by bond pairs and lone pairs of electrons? Illustrate by giving one example of each type.
Solution 1
When two atoms combine by sharing their one or more valence electrons, a covalent bond is formed between them.
The shared pairs of electrons present between the bonded atoms are called bond pairs. All valence electrons may not participate in bonding. The electron pairs that do not participate in bonding are called lone pairs of electrons.
For example, in C2H6 (ethane), there are seven bond pairs but no lone pair present.
In H2O, there are two bond pairs and two lone pairs on the central atom (oxygen).
Solution 2
The electron pair involved in sharing between two atoms during covalent bonding is called shared pair or bond pair. At the same time, the electron pair which is not involved in sharing is called lone pair of electrons.
For example, In `CH_4` 
there are only 4 bond pairs, but in `H_2O`, 
there are two bond pairs and two lone pairs
