Why the bond angle in ammonia is 107 and that in water is 104 while both of them are sp3 hybridised?

The bond angle in ammonia is 107.5°, whereas in water it is 104.5°, despite the fact that both molecules are sp3 hybridised.

The repulsion force between two lone pairs is larger than that between two bond pairs.

The repulsive forces BP-BP < BP-LP < LP-LP.

Due to the presence of only one lone pair in ammonia, the force of repulsion between the lone pair and bond pair is not very strong, but it is still more than the force of repulsion between bond pair and bond pair, resulting in a bond angle of 107°C.

In contrast, two lone pairs in the water molecule result in a force of repulsion between the lone pairs that is the strongest of the three types, resulting in a lower bond angle of 104°.

Despite being sp3 hybridised like ammonia, the bond angle of a water molecule is 104°35 due to the effect of lone pair on repulsion force.

According to valence shell electron pair repulsion theory, two types of electron pairs are present around the central atom.

1. Lone pair

2. Bond pair

Lone pair and Bond pair Electrons

In simple words, the lone pair is the unshared pair of electrons and the bond pair is the shared pair of electrons.

Trick to find the type of Hybridization in NH3 & H2O

Both nh3 and h2o are sp3 hydridised but how you can easily find out the type of hybridisation. so the simple trick to find out the type of hybridization is to count the total number of lone pairs of electrons and sigma bonds.

If the total number is equal to four hybrid orbitals as you can see in the case of ammonia, we have one lone pair and three sigma bonds resulting in a total of 4 hybrid orbitals indicating sp3 hybridization whereas in the case of water we have 2 lone pair and two sigma bond results in a total of 4 hybrid orbitals indicate sp3 hybridization.

In both NH3 & H2O, the central atom is Sp3 hybridized because NH3 contain 1 lone pair & 3 bond pair (sigma bond) electrons. The lone pair has a greater repulsion Which compresses the bond pairs to an angle Of 107.5, resulting in a trigonal pyramidal structure.

Whereas the H2O contain 2 lone pair & 2 bond pair of electrons. The lone pairs exert greater repulsion on each other & also on bond pairs. As a result, the bond pairs are compressed together to an angle of 104.5 with an angular shape.

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-> Why are | Bond angles of h20 and nh3 104.5 and 107.5

-> Hybridization Tips & Tricks  

-> What is Sigma bond and pi bond

Frequently Asked Questions – FAQ

What is the hybridisation?

In chemistry, hybridisation is the process of combining atomic orbitals into new hybrid orbitals that are generally of lower energy and ideal for the pairing of electrons to form chemical bonds.

Why bond angle of NH3 is more than that of water though both have sp3 hybridization?

NH3 has a bond angle of 107.5, while H2O has a bond angle of 104.5. The repulsion between a lone pair and a bond pair of electrons is greater than the repulsion between two bond pairs. Due to the presence of a lone pair in NH3, the bond angle is lowered from 109.5′ to 107.5′ as a result of distortion.

How is ammonia sp3 hybridized?

During the production of ammonia, one 2s orbital and three 2p orbitals of nitrogen mix to generate four hybrid orbitals of equivalent energy. This sort of hybridization is referred to as sp3 hybridization.

How is water sp3 hybridized?

During the creation of the water molecule, one 2s orbital and three 2p orbitals of oxygen combine to generate four hybrid orbitals of equal energy. These four new orbitals are referred to as sp3 hybrid orbitals. They are identical in every way.

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