Question

Molecular shapes of ${SF}_{4,}{CF}_4{XeF}_4$ are:

• A. the same with 2, 0, 1 lone pairs of electrons respectively
• B. the same with' 1, 1, 1 lone pair of electrons respectively
• C. the same with 0, 1, 2 lone pairs of electrons respectively
• D. different with 1, 0, 2 lone pairs of electrons respectively

Answer 1

Answer: (D)

different with 1, 0, 2 lone pairs of electrons respectively

Sulphur has 5 lone pair of electrons in isolated state. In the formation of $S{F}_4$, it form bonds with four fluorine atoms. As a result only one lone pair of electron is left with sulphur. Due to 5 lone pair of electrons its geometry should be trigonal bipyramidal. Since two F atoms occupy equatorial position and two occupy axial position, therefore, its shape is see-saw.

Carbon has 4 lone pair of electrons. In the formation of $C{F}_4$, all the four lone pairs are involved in bonding and there are zero lone pair of electrons on carbon. Its shape is tetrahedral.

Xenon has 6 lone pair of electrons. After the formation of $Xe{F}_4$, only two lone pair of electrons are left on xenon. Geometry due to 6 lone pair of electrons should be octahedral, but due to the presence of two lone pair of electrons which occupy axial position, its shape is square planar.