Question

Explain why the bond angle of nh3 is less than that of ch4 although both are sp3 hybridised

Answer 1

All three molecules have four pairs of electrons around their central atom.

As a result, they all have a tetrahedral arrangment of electron pairs around the central atom.

The bond angle in methane, CH4, is the tetrahedral angle, i.e. 109.5º (109º 28').

Ammonia, NH3, contains a lone pair of electrons, which repels the bonding electrons to give a bond angle of 107º. The atoms have a trigonal pyramidal arrangement.

Water, H2O, contains two lone pairs of electrons, which repel each other as well as the bonding electrons, to give a bond angle of 104.5º. The atoms have a bent line arrangement.

The lone pairs of electrons show up as a small ball on these models. The molecules are animated, but if you want to stop them, right-click to bring up the menu and deselect Animate. Try using the left mouse button to turn the models around in different directions.