Question

Explain VSEPR theory. Applying this theory to predict the shapes of IF₇ and SF₆.

Answer 1

Lewis’s concept of the structure of molecules deals with the relative position of atoms in the molecules and sharing of electron pairs between them. However, we cannot predict the shape of the molecule using Lewis concept. Lewis theory in combination with VSEPR theory will be useful in predicting the shape of molecules.

IF₇:

Iodine has 7 valence electrons in the valence shell. In an excited state it has 6 valency electrons by 1st and 2nd excited state & under sp³d², hybridization and combines with 7 Fluorine to get pentagonal bipyramidal shape. There are no lone pairs.

I = ns² np⁵ nd⁰

pentagonal bipyramidal

SF₆:

Sulphar attain six valence electron in 1st and 2nd excited states undergoes sp³d² hybridization and combines with six ‘F’ atoms, as there no lone pair electrons it geometry in octahedral.

S = 16 = ns² np⁴ nd⁰

Octahedral