Why the bond angle of ammonia is less than methane although they have sp3 hybridisation?
Answers
The bond formation can be undestold by Valence Shell Electron pair Repulsion Model.
The structure of the compound depends upon the number of active set of electrons (The bonded and the lone pair electrons).
Furthermore, there exists repulsion between the bond pairs. And this repusion is greater in lone pair sharing as compares to Valance electrons sharing.
Due to the presence of lone parir in Ammonia(Nitrogen), the bond angle is reduced as due to greater repulsion, whereas in methane(Carbon) there exist no lone pair to repel.
CH4 has bond angle of 109.5 and NH3 has 107.6 something.
In CH4 there is hybridization of sp3 where only four bonding electron pair are present whereas in NH3, despite being sp3 hybridized, have three bonding electron pair and one lone pair. According to VSEPR theory lone pair - bond pair repulsions comes to play which results in decrease of ideal bond angle of tetrahedral geometry.