Concept: The bond angle in molecules with a central atom and two bonded atoms, like H₂O, F₂O, and Cl₂O, is primarily determined by the electronegativity of the surrounding atoms and the size of the central atom's lone pair orbitals. The central atom in all these molecules is oxygen, which has two lone pairs and forms two single bonds, resulting in a bent molecular geometry.

Why (C) is correct:

• The bond angle in these molecules is influenced by the electronegativity of the atoms bonded to oxygen. As the electronegativity of the bonded atoms increases, the bond pair electrons are pulled closer to the bonded atoms, reducing the electron density around the central oxygen atom. This decreases the repulsion between the bond pairs, allowing the lone pair-bond pair repulsion to dominate more effectively, which tends to compress the bond angle.
• Conversely, if the bonded atoms are less electronegative, the bond pair electrons are closer to the central oxygen atom, increasing electron density around oxygen. This leads to greater bond pair-bond pair repulsion, which tends to increase the bond angle.
• Comparing F, H, and Cl: Electronegativity order is F > Cl > H.
• Therefore, the bond pair electrons will be pulled most strongly by F, then by Cl, and least by H.
• This means the bond angle will be smallest for F₂O, followed by H₂O, and largest for Cl₂O.
• The observed bond angles are approximately: F₂O (≈ 103.2°), H₂O (≈ 104.5°), Cl₂O (≈ 110.9°).
• Thus, the increasing order of bond angle is F₂O < H₂O < Cl₂O.

Option Analysis:

• A) F₂O < Cl₂O < H₂O: Incorrect. This order does not follow the electronegativity trend.
• B) Cl₂O < H₂O < F₂O: Incorrect. This is the reverse of the correct order.
• C) F₂O < H₂O < Cl₂O: Correct. This order aligns with the electronegativity effect on bond angles.
• D) H₂O < F₂O < Cl₂O: Incorrect. H₂O has a larger bond angle than F₂O.

Correct Answer: (C)