The central atoms of the three substances are all sp3 hybrid, and the hybrid orbitals are all regular tetrahedrons.

Among them, CH4 is isotropic hybrid, and all four hybrid orbitals are bonding electrons, and the bond angle = tetrahedral bond angle = 109 28'.

NH3 and H2O are unequal hybrids, and the central atoms N and O have 65,438+0 and 2 hybrid orbital-filled lone pairs, respectively. The repulsive force of lone pair is greater than that of bonding electron, so the bond angle is compressed. The more lone pair number, the greater the repulsive force and the smaller the bond angle is compressed.

NH3 bond angle 107 18'

H2O bond angle 104.5.