Question

In the structure of ${\mathrm{ClF}}_3$ the number of lone pairs of electrons on central atom $\mathrm{Cl}$ is :

• A. One
• B. Two
• C. Three
• D. Four

Answer 1

The correct option is B

Two

Explanation for the correct answer:-

Option (B):- Two

Structure of Chlorine trifluoride:-

1. It follows the VSEPR theory.
2. Valence shell electron pair repulsion (VSEPR) is actually a model-based theory which is used for the prediction of 3-D molecular geometry and this all is actually based on the valence shell electron bond pairs among all the atoms in a molecule.
3. The pairs of electrons which are there in bonds and lone pairs will repel each other according to VSEPR theory. And here, covalent bonds are formed because of the sharing of electrons and these covalent bonds will arrange themselves around the main central atom.
4. Chlorine trifluoride $\left({\mathrm{ClF}}_3\right)$ has 10 electrons around the central chlorine atoms.
5. The highest repulsion present is between any two lone electron pairs, which results in moving them apart as far as possible.
6. The two lone pairs occupy an equatorial position at an angle of $120°$ to each other, this gives the lowest energy arrangement of electrons pairs in the molecules.
7. So, they have 5 electron pairs arranged in a trigonal bipyramidal shape.
8. There's $175°$ $\mathrm{F}-\mathrm{Cl}-\mathrm{F}$ bond angle present.
9. Two equatorial lone pairs make the final structure which is T-shaped.
10. The formula used for predicting the structure of any molecule and finding the total number of electrons around the central atom:

$$\begin{gathered} \mathrm{Hybrid}\mathrm{no}.=\mathrm{No}.\mathrm{of}\mathrm{lone}\mathrm{pairs}+\mathrm{No}.\mathrm{of}\mathrm{bond}\mathrm{pairs} \\ =\mathrm{No}.\mathrm{of}\mathrm{lone}\mathrm{pairs}+\mathrm{No}.\mathrm{of}\mathrm{\sigma }\mathrm{bonds}. \\ \mathrm{H}=\frac{1}{2}[\mathrm{V}+\mathrm{M}-\mathrm{C}+\mathrm{A}] \end{gathered}$$

where,

H = Hybrid No.

V = No. of valence electron on the central atom

M = No. of Monovalent atoms/groups directly attached to central atom. ( $\mathrm{M}=\mathrm{R},\mathrm{OR},\mathrm{Ar},\mathrm{OH},\mathrm{H},\mathrm{X}$ )

C = Charge on cation

A = Charge on Anion

Therefore, the correct option is (B):- Two.