posted by Abhishek kumar sahi .
Explain why bond angle of water is 104' and bond angle of NH3 is 107' both less than tetrahedral bond angle? Explain
Look at the Lewis dot structure. H2O has two sets of lone pairs of electrons and NH3 has one set. Lone pairs tend to occupy more space; therefore, the lone pairs push the remaining atoms (H atoms in this case) closer together in H2O and NH3 so the angle is less than the 109 and 28' of the tetrahedral angle.
You (Abhishek) seem to be using ' (arc minutes) where the units should be degrees