What are lone pairs and how do they affect bonding?

Lone pairs are valence electrons that are not involved in bonding and remain on an atom. They influence molecular shape and polarity due to their repulsion effects. For example, in water (H₂O), oxygen has two lone pairs, causing a bent shape instead of linear. Lone pairs can participate in reactions, like forming coordinate covalent bonds. They also increase electron-electron repulsion, affecting bond angles. In ammonia (NH₃), the lone pair on nitrogen gives the molecule a trigonal pyramidal shape. Understanding lone pairs is essential in predicting geometry via VSEPR theory.