Chapter U2.10, Problem 4E

Interpretation Introduction

Interpretation: The three dimensional structure of H₂S needs to be explained.

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.

Hybridization of any atom indicates the molecular geometry of molecule. The formula to check the hybridization can be written as:

Hybridization = Number of sigma bonds + Number of lone pair

The molecular geometry of molecules with lone pair on central atom is given by VSEPR theory.

Answer to Problem 4E

The three dimension structure of H₂S is bent or V-shape with bond angle less than 109°.

Explanation of Solution

For Lewis structure of H₂S molecule, calculate total number of valence electrons:

H₂S molecule = 6 electrons in S + 1 x 2 valence electrons in H = 8 electrons

Hybridization = Number of sigma bonds + Number of lone pair

Hybridization of S atom = 2 + 2 = 4 = sp³

Thus, with sp³ hybridization, the molecular shape must be tetrahedral but due to presence of two lone pair on central S atom, the geometry must be changed in such a way that the repulsion between lone pair and bond pair must be least. Therefore the molecular geometry changes to bent shape with bond angle less than 109°.

Conclusion

The presence of lone pair on central atom changes the molecular geometry of molecule.