Chapter 11, Problem 13STP

Interpretation Introduction

Interpretation:

The molecular shape of hydrogen sulfide should be selected from the given shapes.

Concept introduction:

The geometric shape of the molecule is predicted by VSEPR theory (Valence shell electron pair repulsion theory) from electron pairs surrounding the central atom of the molecule whereas the molecular shape of the molecule is predicted by number of electron pairs as well as lone pairs.

Answer to Problem 13STP

The correct option is (A):

Explanation of Solution

Given:

The Lewis structure of hydrogen sulfide, ${\text{H}}_{\text{2}}\text{S}$ is drawn as:

For drawing the Lewis structure of ${\text{H}}_{\text{2}}\text{S}$ :

• Calculate the total number of valence electrons in molecule ${\text{H}}_{\text{2}}\text{S}$:

Total number of valence electrons = 2(valence electrons of H) + (valence electrons of S)

$=2(1)+(6)={\text{8 e}}^{-}$

• Arrange the atoms in such a way that the least electronegative atom is at the center. Then put the valence electrons around them such that each atom contributes at least 1 electron to single bond and the octet rule for each atom is followed.
• To complete the octet each hydrogen, H atoms forms single bond with sulfur, S. The rest number of electrons are present as lone pair on sulfur atom, the number of lone pair of electrons = Total number of valence electrons − Total number of electrons involved in bond formation.

The number of lone pair of electrons = 8 − 4 = 4 electrons

The Lewis structure for ${\text{H}}_{\text{2}}\text{S}$ is:

Since, in the Lewis structure of ${\text{H}}_{\text{2}}\text{S}$ there are 2 electron pairs and 2 lone pairs so, the electron pair arrangement is tetrahedral and molecular shape is bent so, the correct molecular shape of hydrogen sulfide is:

Hence, the correct option is (A):