Question

Choose the molecules in which hybridization occurs in ground state?
A. $BC{l}_3$
B. $N{H}_3$
C. $Be{F}_2$
D. $PC{l}_3$

Answer 1

Hint:In order to identify the compounds where hybridization takes place at ground state the compounds that have half-filled orbital will undergo hybridization in the ground state. So, we must know the electronic configuration of each of the compounds to solve this question.

Complete step by step answer:
In the following question, the most fitting first step would be to write down the electronic configuration of each central atom.
Taking the first compound, that is, boron trichloride. Here, boron is the central atom. Boron has 5 electrons that arrange themselves in such a way that the $2p$ orbital of boron contains $1$ electron. The geometry of $BC{l}_3$ is a Trigonal planar shape. This shape is formed when boron is in $s{p}^2$ state; this means that hybridization occurs in the first excited state where an electron from the $2s$ orbital jumps to the $2p$ orbital.
Next is ammonia. In this compound we understand that the geometry of the compound is tetrahedral. Nitrogen has the electronic configuration of $1s^{2}2s^{2}2p^3$ . This means that it forms bonds with hydrogen without undergoing any excitation.
In beryllium fluoride, we can write the electronic configuration of Beryllium in the following manner $1s^{2}2s^2$ .
This means that it will require excitation to become hybridized as the orbitals are completely filled. The hybridization of $Be$ is $sp$ .
For phosphorus trichloride, the electronic configuration is represented in the following manner $1s^{2}2s^{2}2p^{6}3s^{2}3p^3$ . This shows that the $p$ orbital of phosphorus is half filled which implies that it does not require any excitation to form bonds with chlorine and can do so in the ground state itself. We also recall that the hybridization of this compound is $s{p}^3$ .
So, to answer this question, we can say that ammonia and phosphorus trichloride are the two compounds that can undergo hybridization in the ground state.

Note:
Hybridization refers to the mixing of atomic orbital into a new orbital suitable for the pairing of electrons to form covalent bonds in valence bond theory. Hybrid orbitals are useful in the explanation of molecular geometry and atomic bonding properties and are symmetrically disposed in space. Usually hybrid orbitals are formed by mixing atomic orbitals of comparable energies.