Question

Draw shape of the following molecules on the basis of VSEPR theory $XeF_{4}$ and $SF_{4}$ (At. No. of Xe = 54, At. No of S = 16).

Answer 1

"Valence Shell Electron Pair Repulsion" (VSEPR) theory:

· This theory was proposed by Sedgwick and Powell and developed by "Nyholm and Gillespie".

· States that the orbitals present in the valence shell of central atom should be arranged in space in such a way that they lie as far away from each other, so that repulsion between them is minimum and stability is maximum.

· The electron pair present in the "valance shell" of atom and it is "not involved" in the bonding, called Lone pair.

· Electron pair involved in bonding, called Bond pair.

· According to the VSEPR theory order of repulsions between electron pairs are as follows, lon pair-lone pair > lone pair-bond pair > Bond pair-bond pair.

· Depending upon the amount of lone pairs present at the central atom shape of molecule  varies.

VSEPR structure of $Xe{ F }_{ 4 }$ is planar in square. It is an octahedral but due to the 2 lone pairs of this molecule have square planar shape.

$S{ F }_{ 4 }$ shape of the molecule is trigonal and bipyramidal.