Question

The number of lp-bp repulsions present in $Cl{F_3}$ at nearly $90$ degree angle are _________ .

Answer 1

$Cl{F_3}$ is a chemical compound composed of chlorine and fluorine. It is an inorganic compound. The structure can be determined with the help of VSEPR theory.

Complete step by step answer:
VSEPR theory is the abbreviation of Valence Shell Electron Pair repulsion theory. This theory is used to determine the shape of the molecules by considering the number of electrons around the central atom.
As the name suggests, only the valence shell electrons are considered for elucidation of the structure. The theory says that the valence electrons whether bonded or non-bonded are arranged in such a way so as to minimize the electron pair repulsion. The repulsion varies in the order lone pair-lone pair > lone pair-bond pair > bond pair-bond pair electrons.
Out of chlorine and fluorine the less electronegative atom is chlorine, so it is the central atom of the given molecule. Chlorine is an atom in the periodic table with atomic number$17$. The electronic configuration of chlorine is
$S:1{s^2}2{s^2}2{p^6}3{s^2}3{p^5}$
The valence shell of chlorine is $3$which contains a total of $7$electrons, two in $3s$ and five in$3p$. A total of three fluorine atoms are bonded to the central atom by sharing one electron. So the three electrons of the central atom bonded to three fluorine atoms by sharing one electron each between the bonded atoms leaving behind four electrons non-bonded.
The VSEP number = $\dfrac{1}{2}$ (number of electrons around the central atom + number of electron from three fluorine atoms)
$= \dfrac{1}{2}\left( {7 + 3} \right) = 5$ .
The VSEP number equal to five belongs to the shape trigonal bipyramidal. Out of the five corners of the geometry two are occupied by the lone pair of electrons of the central atom chlorine. The other three corners are occupied by the three fluorine atoms. Thus the structure of $Cl{F_3}$ is T-shaped with a lone pair in the equatorial plane. Each lone pair in the molecule is forming nearly $90$degree angle with axial fluorine.

Hence, the number of lp-bp repulsions present in $Cl{F_3}$= 4.

Note:
The VSEPR theory fails to explain the structure of transition metal complexes as it did not consider the size of the substituents attached to the central atom. Knowing the geometry of the molecule helps in understanding the reactions of the molecule.