Chapter 9, Problem 9.69QP

(a)

Interpretation Introduction

Interpretation: The geometry of the given cation and the bonding of $\text{C}-\text{N}$ according to valence bond theory, the molecular geometry of the given anion and the Lewis structure of the given anion is to be identified.

Concept introduction: The Lewis structure represents all bonding and non-bonding electrons surrounding the atoms involved in a molecule. A molecule exhibits a particular geometry in space considering the steric hindrances of the bond pairs and the lone pairs of electron.

Valence bond theory determines the chemical bonding in a molecule.

To determine: The geometry of the given cation and the bonding of $\text{C}-\text{N}$ according to valence bond theory.

Answer to Problem 9.69QP

Solution

The geometry of $\left[{\left({\text{CH}}_{\text{3}}\right)}_{\text{4}}{\text{N}}^{+}\right]$ is tetrahedral and the bond angle between them is $109°$.

The hybridization of the $\left[{\left({\text{CH}}_{\text{3}}\right)}_{\text{4}}{\text{N}}^{+}\right]$ is $s{p}^3$.

Explanation of Solution

Explanation

The electronic geometry of the molecule is determined by the number of electron groups bonded to the central atom.

The Lewis structure of the tetramethylammonium $\left[{\left({\text{CH}}_{\text{3}}\right)}_{\text{4}}{\text{N}}^{+}\right]$ is,

Figure 1

From the above figure it is concluded that, there are four electron groups.

According to VBT theory, the molecules that have four electron groups around the central atom have tetrahedral geometry and the bond angle between them is $109°$.

Therefore, the geometry of $\left[{\left({\text{CH}}_{\text{3}}\right)}_{\text{4}}{\text{N}}^{+}\right]$ is tetrahedral and the bond angle between them is $109°$.

The hybridization of the $\left[{\left({\text{CH}}_{\text{3}}\right)}_{\text{4}}{\text{N}}^{+}\right]$ is $s{p}^3$.

(b)

Interpretation Introduction

To determine: The Lewis structure of the anion consistent with the given bond length.

Answer to Problem 9.69QP

Solution

The Lewis structure of ${\text{SO}}_2{\text{F}}_3{}^{-}$ is given in figure 2.

Explanation of Solution

Explanation

The atomic number of $\text{S}$ is $16$.

The electronic configuration of $\text{S}$ is,

$\left[\text{Ne}\right]{\text{3p}}^{\text{2}}{\text{3p}}^{\text{4}}$

The number of valence electrons of $\text{S}$ is $6$.

The atomic number of $\text{O}$ is $8$.

The electronic configuration of $\text{O}$ is,

${\text{1s}}^{\text{2}}{\text{2p}}^{\text{2}}{\text{2p}}^{\text{4}}$

The number of valence electrons of $\text{O}$ is $6$.

The atomic number of $\text{F}$ is $9$.

The electronic configuration of $\text{F}$ is,

${\text{1s}}^{\text{2}}{\text{2p}}^{\text{2}}{\text{2p}}^5$

The number of valence electrons of $\text{F}$ is $7$.

The total number of valence electrons of ${\text{SO}}_2{\text{F}}_3{}^{-}$ is,

$6+2\times 6+3\times 7=39$

The Lewis structure of ${\text{SO}}_2{\text{F}}_3{}^{-}$ is,

Figure 2

The bond lengths of both $\text{S}-\text{O}$ is $\text{146}\text{pm}$. This concluded that both the $\text{S}-\text{O}$ bonds are equivalent and are taking part in resonance. The bond length is between the single and double bond of sulphur and oxygen atom.

The resonating structure of ${\text{SO}}_2{\text{F}}_3{}^{-}$ is,

Figure 3

(c)

Interpretation Introduction

To determine: The molecular geometry of the given anion.

Answer to Problem 9.69QP

Solution

The geometry of ${\text{SO}}_2{\text{F}}_3{}^{-}$ is trigonal bipyramidal.

Explanation of Solution

Explanation

From the figure 2, it is concluded that, in the anion ${\text{SO}}_2{\text{F}}_3{}^{-}$ are five electron groups.

According to VBT theory, the molecules that have five electron groups around the central atom have trigonal bipyramidal geometry and the bond angle between $\text{F}-\text{S}-\text{F}$ is $120°$ and the bond angle between $\text{F}-\text{S}-\text{O}$ is $90°$ because sulphur-oxygen atom is perpendicular to sulphur and fluorine bond.

Therefore, the geometry of ${\text{SO}}_2{\text{F}}_3{}^{-}$ is trigonal bipyramidal.

The hybridization of the ${\text{SO}}_2{\text{F}}_3{}^{-}$ is $s{p}^{3}d$.

Conclusion

(a)

• The geometry of $\left[{\left({\text{CH}}_{\text{3}}\right)}_{\text{4}}{\text{N}}^{+}\right]$ is tetrahedral and the bond angle between them is $109°$.
• The hybridization of the $\left[{\left({\text{CH}}_{\text{3}}\right)}_{\text{4}}{\text{N}}^{+}\right]$ is $s{p}^3$.

(b)

• The Lewis structure of ${\text{SO}}_2{\text{F}}_3{}^{-}$ is given in figure 2.

(c)

• The geometry of ${\text{SO}}_2{\text{F}}_3{}^{-}$ is trigonal bipyramidal.