How do lone electron pairs on the central atom affect the molecular shape of a molecule?

• A. They have no effect on the molecular shape and do not influence bond angles.
• B. They attract bonding pairs, increasing bond angles and making the geometry more symmetrical.
• C. They repel bonding pairs, causing bond angles to decrease and altering the ideal geometry.
• D. They only affect the polarity of the molecule, not its shape.

Answer: (C)

Verified step by step guidance

1. Understand that lone electron pairs are pairs of valence electrons localized on the central atom that are not involved in bonding with other atoms.
2. Recall that electron pairs, whether bonding or lone pairs, repel each other due to their negative charge, according to the VSEPR (Valence Shell Electron Pair Repulsion) theory.
3. Recognize that lone pairs occupy more space around the central atom than bonding pairs because lone pairs are held closer to the nucleus and are not shared between atoms, leading to stronger repulsion.
4. Because lone pairs repel bonding pairs more strongly, they push the bonding pairs closer together, which decreases the bond angles between bonded atoms compared to the ideal geometry without lone pairs.
5. Conclude that the presence of lone pairs on the central atom alters the molecular shape by distorting bond angles and changing the idealized geometry predicted by only considering bonding pairs.