Three hydrides of the second-period elements—water (H2O), ammonia (NH3), and methane (CH4)—exhibit different H–X–H bond angles even though each central atom is surrounded by four total electron domains. Use these molecules as a comparative case study to analyze factors that control bond-angle magnitude.
(1) Part 1: For each molecule, state (i) the electron-domain geometry and (ii) the hybridization of the central atom.
(2) Part 2: Arrange the three molecules in order of increasing H–X–H bond angle. Include a reasonable numerical estimate (±2∘) for each angle.
(3) Part 3: Provide a detailed explanation for the trend you reported in part (b), citing the relative strengths of repulsions among lone-pair and bonding-pair electron domains.