Chapter 8.5, Problem 77SSC

Interpretation Introduction

Interpretation:

The Lewis structures of SF₄ and SF₆ molecules needs to be determined by interpreting the polarity.

Concept introduction:

The Lewis structure of an organic compound represents the bonding of atoms with lone pairs (if any). It indicates the bonds with atoms and also arrangement of atoms in molecule. The polarity of molecule can be determined by the arrangements of bonded atoms in the molecule.

Answer to Problem 77SSC

Polar molecule

Non-polar molecule

Explanation of Solution

In the SF₄ molecule, Satom contains 6 valence electrons and F has 7 valence electrons. The total number of valence electron can be determined in it as follows:

Number of valence electron = Number of atom S (valence electron in S) + Number of atom F (valence electron in F) = $\text{(1}\times \text{6) + (4}\times \text{7) = 34}$

Hence the Lewis structure must be:

$\begin{array}{l}\text{Hybridization = Number of sigma bonds + Number of lone pairs on bonded atoms}\\ {\text{Hybridization = 4 + 1 = sp}}^{\text{3}}\text{d }\end{array}$

Since the standard geometry must be trigonal bipyramid yet the geometry changes to see-saw due to presence of one lone pair on S atom.

Since the polarity directions are towards F atom therefore overall it is a polar molecule.

In the SF₆ molecule, S atom contains 6 valence electrons, and F has 7 valence electrons. The total number of valence electron can be determined in it as follows:

Number of valence electron = Number of atom S (valence electron in S) + Number of atom F (valence electron in F) = $\text{(1}\times \text{6)+ (6}\times \text{7) = 48}$

Hence the Lewis structure must be:

$\begin{array}{l}\text{Hybridization = Number of sigma bonds + Number of lone pairs on bonded atoms}\\ {\text{Hybridization = 6 + 0 = sp}}^{\text{3}}{\text{d}}^{\text{2}}\text{ = octahedral}\end{array}$

Due to symmetrical structure of molecule it is non-polar molecule.

Conclusion

Thus,