Chapter U3.1, Problem 6E

(a)

Interpretation Introduction

Interpretation: The structural formulas of nitrogen, oxygen, carbon dioxide and water vapor needs to be drawn including the lone pair of electrons.

Concept Introduction :

To draw the structural formulas and Lewis dot structure of the molecules, count the total number of valence electrons of all the constituent atoms.

Arrange the electrons around each atom in such a way that each atom should get eight electrons around it.

Lone pair of electrons does not participate in chemical bonding.

Due to the presence of lone pair of electrons, the molecule deviates from its regular shape and exhibits polarity.

Explanation of Solution

Nitrogen structure N₂:

The total number of valence electrons in N₂ is 5+5 = 10

Structure of N₂:

Nitrogen is a linear molecule.

Oxygen: Total number of valence electrons in oxygen is 6+6 =12.

Arrange these electrons in such a way that each atom should be surrounded by eight electrons.

Oxygen is a linear molecule.

Water Vapor:

Valence electrons in oxygen atom are 6.

Hydrogen has one valence electron.

Total water has 6+2=8 electrons.

Arrange them in such a way that oxygen should get 8 electrons around it and hydrogen should get two electrons.

Water has bent shape.

Carbon dioxide:

Carbon has four valence electrons.

Oxygen has six valence electrons.

Total number of valence electrons = 4+ 6+6=16 electrons.

Structure of CO₂:

Carbon dioxide is a linear molecule.

(b)

Interpretation Introduction

Interpretation: The Lewis structure of water needs to be drawn.

Concept Introduction: To draw Lewis dot structure of water, count the total number of valence electrons of all the constituent atoms.

Then, arrange the electrons around each atom in such a way that oxygen should have eight electrons and hydrogen has two electrons.

Explanation of Solution

Valence electrons in oxygen atom are 6.

Hydrogen has one valence electron.

Total water has 6+2=8 electrons.

Arrange them in such a way that oxygen should get 8 electrons around it and hydrogen should get two electrons.

(c)

Interpretation Introduction

Interpretation: Polar and non-polar molecules among nitrogen, oxygen, water and carbon dioxide needs to be determined.

Concept Introduction:

In Lewis dot structure the central atoms that carry lone pair of electrons are polar.

Explanation of Solution

Nitrogen is a polar molecule, since nitrogen has a lone pair.

Oxygen is a polar molecule, since oxygen has two lone pairs of electrons.

Water is a polar molecule, since oxygen has two lone pairs of electrons.

Carbon dioxide is a nonpolar molecule, since dipole moment of C-O polar bond cancels on each direction.

(d)

Interpretation Introduction

Interpretation: Natural occurrence of these molecules needs to be explained.

Concept Introduction:

The molecules which have strong intermolecular forces of attraction can exist as solids and then liquid and weak intermolecular forces of attraction make them exist as gases.

Explanation of Solution

Water exists as a liquid at room temperature due to strong H-bond.

Nitrogen, oxygen and carbon dioxide exist as gases under normal conditions.