Chapter 2, Problem 2.27E

(a)

Interpretation Introduction

Interpretation:

The Lewis structures of ${\text{CH}}_3{}^{+}$, ${\text{CH}}_4$, ${\text{CH}}_3{}^{-}$ , ${\text{CH}}_2$, ${\text{CH}}_2{}^{2+}$ and ${\text{CH}}_2{}^{2-}$ to be drawn.

Concept Introduction:

Lewis structures represent covalent bonds and describe valence electrons configuration of atoms. The covalent bonds are depicted by lines, and unshared electron pairs by pairs of dots. The sequence to write Lewis structure of some molecule is given as follows:

• The central atom is identified and various other atoms are arranged around it. This central atom so chosen is often the least electronegative.
• Total valence electrons is estimated for each atoms.
• single bond is first placed between each atom pair.
• The electrons left can be allocated as unshared electron pairs or as multiple bonds around the symbol of elemnt to satisfy the octet (or duplet) for each atom.
• Add charge on overall structure in case of polytatomic cation or anion.

(b)

Interpretation Introduction

Interpretation:

Whether the carbon atoms in ${\text{CH}}_3{}^{+}$, ${\text{CH}}_4$, ${\text{CH}}_3{}^{-}$ , ${\text{CH}}_2$, ${\text{CH}}_2{}^{2+}$ and ${\text{CH}}_2{}^{2-}$ are radical or not has to be identified.

Concept Introduction:

Refer to part (a).

(c)

Interpretation Introduction

Interpretation:

The species ${\text{CH}}_3{}^{+}$, ${\text{CH}}_4$, ${\text{CH}}_3{}^{-}$ , ${\text{CH}}_2$, ${\text{CH}}_2{}^{2+}$ and ${\text{CH}}_2{}^{2-}$ have to be arranged in increasing $\text{HCH}$ bond angle.

Concept Introduction:

• single bond is always associated with sigma bonds. Molecules that have all atoms connected by sigma bond exclusively are stated to be in $s{p}^3$ hybridization. It has bond angle of $109.5°$.
• double bond and carbocation are associated with $s{p}^2$ hybridization. It has bond angle of $120°$.
• triple bond is always associated with $sp$ hybridization. It has bond angle of $180°$.