Here are the essential concepts you must grasp in order to answer the question correctly.
Molecular Geometry
Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. The shape of a molecule is determined by the repulsion between electron pairs surrounding the central atom, which influences bond angles. For ammonia (NH3), the geometry is trigonal pyramidal, leading to a specific H-N-H bond angle that can be compared to other species like the amide ion and ammonium ion.
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Molecular Geometry with Two Electron Groups
Hybridization
Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate bonding. In ammonia (NH3), the nitrogen atom undergoes sp3 hybridization, resulting in a bond angle of approximately 107 degrees. In contrast, the ammonium ion (NH4+) has sp3 hybridization as well, but the bond angles are closer to 109.5 degrees due to the absence of lone pairs, while the amide ion (NH2-) has a different hybridization affecting its bond angles.
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Lone Pairs and Bond Angles
Lone pairs of electrons can significantly affect bond angles in a molecule. They occupy more space than bonding pairs, causing bond angles to decrease. In the case of ammonia, the presence of one lone pair results in a smaller H-N-H bond angle compared to the ammonium ion, which has no lone pairs, leading to larger bond angles. The amide ion, with two lone pairs, will have the smallest bond angle due to increased repulsion.
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