Chapter U2.5, Problem 7E

(a)

Interpretation Introduction

Interpretation:

Lewis dot structures for C₂H₂, N₂H₄and H₂O₂ must be drawn and the pattern must be explained.

Concept Introduction :

Lewis dot structure is the representation of a molecule using valence electrons shown as dots.

Answer to Problem 7E

Lewis dot structures for C₂H₂, N₂H₄and H₂O₂ are given below.

  

Carbon has formed triple bond, nitrogen has formed double bond and oxygen has formed single bond.

Explanation of Solution

In C₂H₂, two triple bonded C atoms are central atoms which are bonded to 1 H. In N₂H₂, two double bonded N atoms are central atoms which are bonded to 1H. There is one lone pair of electrons ion each N atom. In H₂O₂, two single bonded O atoms are central atoms which are bonded to 1H. There are two lone pairs of electrons on each O atom.

(b)

Interpretation Introduction

Interpretation:

Two ways must be mentioned to check whether the Lewis structures are correct or not.

Concept Introduction :

Whether a Lewis dot structure is correct or not can be checked using HONC rule as per which H, O, N and C form 1, 2, 3 and 4 bonds respectively.

Answer to Problem 7E

All the Lewis structures are correct as per HONC 1234 rule and octet rule.

Explanation of Solution

In C₂H₂ each carbon has total 4 bonds and each hydrogen has 1 bond thus it is correct as per HONC 1234 rule. Each carbon atom is octet that is there are eight electrons. Hydrogen atom is duplet.

In N₂H₄ each N atom has total 3 bonds and one lone pair of electrons. Thus it is correct as per HONC 1234 rule. Each nitrogen attains octet and each hydrogen is duplet.

In H₂O₂ each oxygen has total two bonds and two lone pairs of electrons. Each hydrogen has 1 bond. Thus it is correct as per HONC 1234 rule. Each oxygen atom attains octet and each hydrogen is duplet.