Chapter 8, Problem 85E

Write Lewis structures that obey the octet rule (duet rule for H) for each of the following molecules. Carbon is the central atom in CH₄, nitrogen is the central atom in NH₃, and oxygen is the central atom in H₂O.

a. F₂

b. O₂

c. CO

d. CH₄

e. NH₃

f. H₂O

g. HF

Interpretation Introduction

Interpretation: The Lewis structure is to be drawn for the given molecules.

Concept introduction: The Lewis structure is also known as dot structure. This structure depicts the bonding between atoms and the lone pairs of electrons if exists.

The octet rule states that atoms or molecules gain or lose electrons to get the electronic configuration of nearest noble gas.

To determine: The Lewis structure of the molecule ${\text{F}}_2$.

Answer to Problem 85E

Explanation of Solution

The first step in determining the Lewis structure is to determine the number of valence electrons. The atomic number of fluorine $\left(\text{F}\right)$ is 9 and its electronic configuration is,

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

The valence electron of fluorine is 7

The fluorine molecule ${\text{F}}_2$ is made of two fluorine atoms; hence, the total number of valence electrons is,

$\begin{array}{c}\text{F}\text{+}\text{F}\text{=}\text{7+7}\\ \text{=14}\end{array}$

The skeletal structure of ${\text{F}}_2$ is,

$\text{F}-\text{F}$

Each fluorine atom requires one electron to complete the octet. Hence, the mutual sharing of two electrons takes place. The 12 valence electrons present are placed as lone pairs in such a way that each atom gets three lone pairs.

The Lewis structure of ${\text{F}}_2$ is

Figure 1

Interpretation Introduction

Interpretation: The Lewis structure is to be drawn for the given molecules.

Concept introduction: The Lewis structure is also known as dot structure. This structure depicts the bonding between atoms and the lone pairs of electrons if exists.

The octet rule states that atoms or molecules gain or lose electrons to get the electronic configuration of nearest noble gas.

To determine: The Lewis structure of the molecule ${\text{O}}_2$.

Answer to Problem 85E

Explanation of Solution

The first step in determining the Lewis structure is to determine the number of valence electrons. The atomic number of oxygen $\left(\text{O}\right)$ is 8 and its electronic configuration is,

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

The valence electron of oxygen is 6

The oxygen molecule ${\text{O}}_2$ is made of two oxygen atoms; hence, the total number of valence electrons is,

$\begin{array}{c}\text{O}\text{+}\text{O}\text{=}\text{6+6}\\ \text{=12}\end{array}$

The skeletal structure of ${\text{O}}_2$ is,

$\text{O}-\text{O}$

Each oxygen atom requires two electrons to complete the octet. Hence, the mutual sharing of four electrons takes place. The 8 valence electrons present are placed as lone pairs in such a way that each atom gets two lone pairs.

The Lewis structure of ${\text{O}}_2$ is

Figure 2

Interpretation Introduction

Interpretation: The Lewis structure is to be drawn for the given molecules.

Concept introduction: The Lewis structure is also known as dot structure. This structure depicts the bonding between atoms and the lone pairs of electrons if exists.

The octet rule states that atoms or molecules gain or lose electrons to get the electronic configuration of nearest noble gas.

To determine: The Lewis structure of the molecule $\text{CO}$.

Answer to Problem 85E

Explanation of Solution

The first step in determining the Lewis structure is to determine the number of valence electrons. The atomic number of oxygen is 8 and its electronic configuration is,

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

The valence electron of oxygen is 6

The atomic number of carbon $\left(\text{C}\right)$ is 6 and its electronic configuration is,

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

The valence electron of carbon is 4

The molecule $\text{CO}$ is made of carbon and oxygen atoms; hence, the total number of valence electrons is,

$\begin{array}{c}\text{C}\text{+}\text{O}\text{=}\text{4+6}\\ \text{=10}\end{array}$

The skeletal structure of $\text{CO}$ is,

$\text{C}-\text{O}$

Each oxygen atom requires two electrons to complete the octet whereas carbon requires four electrons to complete the octet. Hence, the mutual sharing of six electrons takes place which is represented by triple bond. The 4 valence electrons left are placed as lone pairs in such a way that each atom gets one lone pair.

The Lewis structure of $\text{CO}$ is

Figure 3

Interpretation Introduction

Interpretation: The Lewis structure is to be drawn for the given molecules.

Concept introduction: The Lewis structure is also known as dot structure. This structure depicts the bonding between atoms and the lone pairs of electrons if exists.

The octet rule states that atoms or molecules gain or lose electrons to get the electronic configuration of nearest noble gas.

To determine: The Lewis structure of the molecule ${\text{CH}}_4$.

Answer to Problem 85E

Explanation of Solution

The first step in determining the Lewis structure is to determine the number of valence electrons. The atomic number of carbon is 6 and its electronic configuration is,

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

The valence electron of carbon is 4

The atomic number of hydrogen $\left(\text{H}\right)$ is 1 and its electronic configuration is,

${\text{1s}}^1$

The valence electron of hydrogen is 1

The molecule ${\text{CH}}_4$ is made of one carbon and four hydrogen atoms; hence, the total number of valence electrons is,

$\begin{array}{c}\text{C}\text{+}\text{4H}\text{=}\text{4+4}\\ \text{=}\text{8}\end{array}$

The skeletal structure of ${\text{CH}}_4$ is,

Figure 4

Each hydrogen atom requires one electron to complete the octet whereas carbon requires four electrons to complete the octet. In the molecule ${\text{CH}}_4$, carbon is central atom which is placed at the center and hydrogen atoms are arranged on the sides. Hence, the mutual sharing of eight electrons takes place.

The Lewis structure of ${\text{CH}}_4$ is

Figure 5

Interpretation Introduction

Interpretation: The Lewis structure is to be drawn for the given molecules.

Concept introduction: The Lewis structure is also known as dot structure. This structure depicts the bonding between atoms and the lone pairs of electrons if exists.

The octet rule states that atoms or molecules gain or lose electrons to get the electronic configuration of nearest noble gas.

To determine: The Lewis structure of the molecule ${\text{NH}}_3$.

Answer to Problem 85E

Explanation of Solution

The first step in determining the Lewis structure is to determine the number of valence electrons. The atomic number of nitrogen $\left(\text{N}\right)$ is 7 and its electronic configuration is,

${\text{1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^3$

The valence electron of nitrogen is 5

The atomic number of hydrogen is 1 and its electronic configuration is,

${\text{1s}}^1$

The valence electron of hydrogen is 1

The molecule ${\text{NH}}_3$ is made of one nitrogen and three hydrogen atoms; hence, the total number of valence electrons is,

$\begin{array}{c}\text{N}\text{+}3\text{H}\text{=}5\text{+}\text{3}\\ \text{=}\text{8}\end{array}$

The skeletal structure of ${\text{NH}}_3$ is,

Figure 6

Each hydrogen atom requires one electron to complete the octet whereas nitrogen requires three electrons to complete the octet. In the molecule ${\text{NH}}_3$, nitrogen is central atom which is placed at the center and hydrogen atoms are arranged on the sides. Hence, the mutual sharing of eight electrons takes place.

The Lewis structure of ${\text{NH}}_3$ is

Figure 7

Interpretation Introduction

Interpretation: The Lewis structure is to be drawn for the given molecules.

Concept introduction: The Lewis structure is also known as dot structure. This structure depicts the bonding between atoms and the lone pairs of electrons if exists.

The octet rule states that atoms or molecules gain or lose electrons to get the electronic configuration of nearest noble gas.

To determine: The Lewis structure of the molecule ${\text{H}}_2\text{O}$.

Answer to Problem 85E

Explanation of Solution

The first step in determining the Lewis structure is to determine the number of valence electrons. The atomic number of oxygen is 8 and its electronic configuration is,

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

The valence electron of oxygen is 6

The atomic number of hydrogen is 1 and its electronic configuration is,

${\text{1s}}^1$

The valence electron of hydrogen is 1

The molecule ${\text{H}}_2\text{O}$ is made of one oxygen and two hydrogen atoms; hence, the total number of valence electrons is,

$\begin{array}{c}\text{O}\text{+}2\text{H}\text{=}6\text{+}\text{2}\\ \text{=}\text{8}\end{array}$

The skeletal structure of ${\text{H}}_2\text{O}$ is,

Figure 8

Each hydrogen atom requires one electron to complete the octet whereas oxygen requires two electrons to complete the octet. In the molecule ${\text{H}}_2\text{O}$, oxygen is central atom which is placed at the center and hydrogen atoms are arranged on the sides. Hence, the mutual sharing of eight electrons takes place.

The Lewis structure of ${\text{H}}_2\text{O}$ is

Figure 9

Interpretation Introduction

Interpretation: The Lewis structure is to be drawn for the given molecules.

Concept introduction: The Lewis structure is also known as dot structure. This structure depicts the bonding between atoms and the lone pairs of electrons if exists.

The octet rule states that atoms or molecules gain or lose electrons to get the electronic configuration of nearest noble gas.

To determine: The Lewis structure of the molecule $\text{HF}$.

Answer to Problem 85E

Explanation of Solution

The first step in determining the Lewis structure is to determine the number of valence electrons. The atomic number of fluorine is 9 and its electronic configuration is,

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

The valence electron of fluorine is 7

The atomic number of hydrogen is 1 and its electronic configuration is,

${\text{1s}}^1$

The valence electron of hydrogen is 1

The molecule $\text{HF}$ is made of only one fluorine and hydrogen atoms; hence, the total number of valence electrons is,

$\begin{array}{c}\text{F}\text{+}\text{H}\text{=}7\text{+}1\\ \text{=}\text{8}\end{array}$

The skeletal structure of $\text{HF}$ is,

$\text{H}-\text{F}$

Each hydrogen atom requires one electron to complete the octet whereas fluorine requires one electron to complete the octet. Hence, the mutual sharing of eight electrons takes place.

The Lewis structure of $\text{HF}$ is

Figure 10

Conclusion

The Lewis dot structure is drawn to satisfy the octets of atoms. The octet rule states that elements gain or lose electrons to get the nearest noble gas configuration.