Which of the following species would you predict has the largest bond angle?

• A. NH3 (ammonia)
• B. NO2 (nitrogen dioxide)
• C. CH4 (methane)
• D. H2O (water)

Answer: (B)

Verified step by step guidance

1. Recall that bond angles in molecules are influenced by the electron pair geometry around the central atom, which is determined by the number of bonding pairs and lone pairs of electrons according to VSEPR (Valence Shell Electron Pair Repulsion) theory.
2. Identify the molecular geometry and number of lone pairs on the central atom for each species: CH4 has 4 bonding pairs and 0 lone pairs (tetrahedral), NH3 has 3 bonding pairs and 1 lone pair (trigonal pyramidal), H2O has 2 bonding pairs and 2 lone pairs (bent), and NO2 is a bit different as it is a radical with resonance structures and a bent shape but with fewer lone pairs affecting bond angles.
3. Understand that lone pairs repel more strongly than bonding pairs, which tends to compress bond angles between atoms. Therefore, molecules with more lone pairs on the central atom generally have smaller bond angles.
4. Compare the expected bond angles: CH4 (tetrahedral) has bond angles close to 109.5°, NH3 (trigonal pyramidal) has bond angles slightly less than 109.5°, H2O (bent) has bond angles around 104.5°, and NO2, due to its resonance and fewer lone pairs, tends to have a larger bond angle than NH3 and H2O.
5. Conclude that among the given species, NO2 is predicted to have the largest bond angle because it has fewer lone pair repulsions compressing the bond angle compared to NH3 and H2O, and its molecular structure allows for a wider angle than the tetrahedral CH4.