Question

Which of the following molecule does not show tetrahedral shape
(a) CCl₄
(b) SiCl₄
(c) SF₄
(d) CF₄

Answer 1

Hint: An ammonia (NH₃) molecule has sp³ hybridization, and as expected its structure must be tetrahedral. But due to the presence of lone pairs of electrons, it has a pyramidal structure. Similarly, water molecules also have sp³ hybridization but in the presence of lone it has V-shaped structure.

Complete step by step solution:We all know that the geometry of a molecule can easily be determined by the application of the hybridization concept.
Whereas, for the determination of the shape of any given molecule the concept of VSEPR theory is used.
Therefore, to know the correct shape of the given molecule first we will predict the hybridization. After that we will look at the presence of lone pairs of electrons.
The hybridization of a molecule can be calculated by counting the total number of sigma bonds and lone pairs of electrons.
In CCl₄ there are 4 sigma bonds present around the carbon atom. The value of 4 sigma bonds will be equal to sp³ hybridization. Because all the four valence electrons of a carbon atom are engaged in bonding with four chlorine atoms, therefore CCl₄, does not have any lone pair of electrons i.e., it has tetrahedral geometry as well as tetrahedral shape.
Like CCl₄ , the SiCl₄ and CF₄ also contain 4 sigma bonds without any lone pair of electrons. Therefore, they also have tetrahedral geometry as well as tetrahedral shape.
Unlike CCl₄ ,SiCl₄ and CF₄ , In SF₄ molecule the sulphur has six valence electrons, in which four are involved in the formation of sigma bonds with fluorine atoms and the two-electrons remain as an unshared pair of electrons. Therefore, the total sum of sigma bond and lone pairs in SF₄ will be 5. The value of 5 sigma bonds will be equal to sp³d hybridization and the geometry will be trigonal bi-pyramidal. But due to the presence of a lone pair its shape will be see-saw.

Therefore from the above explanation we can say option (c) will be the correct option:

Note: Hybridization is the process of mixing atomic orbitals to produce new hybrid orbitals. These hybrid orbitals have lower energy than unhybridized orbitals. Based on the mixing of orbitals hybridization can be sp, sp², sp³, sp³d and sp³d².