Question

The shape of ammonia molecules:
(A) Distorted tetrahedral
(B) Hexahedral
(C) Pentahedral
(D) None of these

Answer 1

Hint :In order to solve these types of questions we need to know the structural knowledge in three dimensional space and we can say that since there is a lone pair present in N so its shape will transform a little bit from the original shape.

Complete Step By Step Answer:
For solving this question we need to know that the $ N{H_3} $ is an $ s{p^3} $ hybridized molecule. Three hydrogen bonds to the central atom of the ammonia also has a lone pair of electrons.
The central atom of ammonia, which is nitrogen is $ s{p^3} $ hybridized. It is a gas at normal condition and it is called azane. The molecular weight of ammonia is approximate 17g/mol.
This is colorless alkaline gas.
At the beginning we will study the lewis dot structure of ammonia, nitrogen has 5 valence electrons and each hydrogen has 1 electron in its valence shell. So we can say that since the total number of electrons are 8 so valence is satisfied. And the central atom is nitrogen after the three valence electrons of nitrogen have bonded with three hydrogen atoms we still have two electrons left, which results in the lone pair in the nitrogen.
Now let us see the hybridization of the ammonia which is:
 $ 1{s^2}2{s^2}2p_x^12p_y^12p_z^1 $
During the hybridization, one s orbital and three p of nitrogen hybridize to form four hybrid orbitals having equal energy levels, thus making its hybridization $ s{p^3} $ . half three filled $ s{p^3} $ orbitals of nitrogen form a bond with three hydrogens. The forth fully filled hybridized orbitals hold the lone pair of nitrogen.

So the bond angle should have $ {109.5^ \circ } $ and structure should be tetrahedral but since the lone pair is present so there will be a repulsive force between bond pair and lone pair so the angle is distorted to $ {107^ \circ } $ approx, and our structure will be little distorted and our structure will be distorted tetrahedral.
Hence A is correct.

Note :
The main thing here is to consider the lone pair during the hybridization so it is the common mistake done by us not to consider the lone pair due to which the hybridization is changed and we make it trigonal which is wrong.