Chapter 7, Problem 1QAP

a.

Interpretation Introduction

Interpretation: Lewis structure for ${\text{CCl}}_{\text{4}}$ should be drawn.

Concept Introduction:

• Lewis structures are the diagrams that show the bonding between the atoms of the molecules and existing lone pairs of electrons.
• Bonding electrons are those electrons which are shared between the atoms resulting in the formation of bond.
• Non-bonding electrons are the valence electrons of the atom which are not shared with another atom.

Answer to Problem 1QAP

  

Explanation of Solution

1. Calculate the total number of valence electrons in molecule ${\text{CCl}}_{\text{4}}$:

Total number of valence electrons = valence electrons of C +4(valence electrons of Cl)

  $=4+4(7)=32{\text{ e}}^{-}$

2. Arrange the atoms in such a way that the least electronegative atom is at the center. Then put the valence electrons around them such that each atom contributes at least 1 electron to single bond and the octet rule for each atom is followed.
3. To complete the octet each chlorine, Cl atom forms single bond with carbon, C. The rest number of electrons are present as lone pair on chlorine atoms, the number of lone pair of electrons = Total number of valence electrons − Total number of electrons involved in bond formation.
The number of lone pair of electrons = 32 − 8 = 24 electrons

Thus, as C is the least electronegative, it would be the central atom and on arranging all the valence electrons , one gets the Lewis structure of ${\text{CCl}}_{\text{4}}$

4. as:

  

b.

Interpretation Introduction

Interpretation: Lewis structure for ${\text{NCl}}_3$ should be drawn.

Concept Introduction:

• Lewis structures are the diagrams that show the bonding between the atoms of the molecules and existing lone pairs of electrons.
• Bonding electrons are those electrons which are shared between the atoms resulting in the formation of bond.
• Non-bonding electrons are the valence electrons of the atom which are not shared with another atom.

Answer to Problem 1QAP

  

Explanation of Solution

1. Calculate the total number of valence electrons in molecule ${\text{NCl}}_3$:

Total number of valence electrons = valence electrons of N +3(valence electrons of Cl)

  $=5+3(7)=26{\text{ e}}^{-}$

2. Arrange the atoms in such a way that the least electronegative atom is at the center. Then put the valence electrons around them such that each atom contributes at least 1 electron to single bond and the octet rule for each atom is followed.
3. To complete the octet each chlorine, Cl atom forms single bond with nitrogen, N. The rest number of electrons are present as lone pair on chlorine atoms and nitrogen atom, the number of lone pair of electrons = Total number of valence electrons − Total number of electrons involved in bond formation.
The number of lone pair of electrons = 26 − 6 = 20 electrons
4. Thus, as N is the least electronegative, it would be the central atom and on arranging all the valence electrons , one gets the Lewis structure of ${\text{NCl}}_3$ as:

  

c.

Interpretation Introduction

Interpretation: Lewis structure for ${\text{COCl}}_2$ should be drawn.

Concept Introduction:

• Lewis structures are the diagrams that show the bonding between the atoms of the molecules and existing lone pairs of electrons.
• Bonding electrons are those electrons which are shared between the atoms resulting in the formation of bond.
• Non-bonding electrons are the valence electrons of the atom which are not shared with another atom.

Answer to Problem 1QAP

  

Explanation of Solution

1. Calculate the total number of valence electrons in molecule ${\text{COCl}}_2$:

Total number of valence electrons = valence electrons of C + valence electron of O+2(valence electrons of Cl)

  $=4+6+2(7)=24{\text{ e}}^{-}$

2. Arrange the atoms in such a way that the least electronegative atom is at the center. Then put the valence electrons around them such that each atom contributes at least 1 electron to single bond and the octet rule for each atom is followed.
3. To complete the octet each chlorine, Cl atom forms single bond with carbon, C and formation of double bond takes place between carbon and oxygen.

The rest number of electrons are present as lone pair on chlorine atoms and oxygen atom, the number of lone pair of electrons = Total number of valence electrons − Total number of electrons involved in bond formation.

The number of lone pair of electrons = 24 − 8 = 16 electrons

4. Thus, as C is the least electronegative, it would be the central atom and on arranging all the valence electrons , one gets the Lewis structure of ${\text{COCl}}_2$ as:

  

d.

Interpretation Introduction

Interpretation: Lewis structure for ${\text{SO}}_3^{2-}$ should be drawn.

Concept Introduction:

• Lewis structures are the diagrams that show the bonding between the atoms of the molecules and existing lone pairs of electrons.
• Bonding electrons are those electrons which are shared between the atoms resulting in the formation of bond.
• Non-bonding electrons are the valence electrons of the atom which are not shared with another atom.
• For a molecule possessing negative charge, the charge is added to the total number of valence electron count.

Answer to Problem 1QAP

  

Explanation of Solution

1. Calculate the total number of valence electrons in molecule ${\text{SO}}_3^{2-}$:

Total number of valence electrons = valence electrons of S + 3(valence electrons of O) + 2

  $=6+3(6)+2=26{\text{ e}}^{-}$

2. Arrange the atoms in such a way that the least electronegative atom is at the center. Then put the valence electrons around them such that each atom contributes at least 1 electron to single bond and the octet rule for each atom is followed.
3. To complete the octet two oxygen, O atoms forms single bond with sulfur, S out of three oxygen atoms and both the oxygen atoms carries negative charge and one oxygen atom forms a double bond with oxygen.

The rest number of electrons are present as lone pair on sulfur atom and oxygen atoms, the number of lone pair of electrons = Total number of valence electrons − Total number of electrons involved in bond formation.

The number of lone pair of electrons = 26 − 8 = 18 electrons

4. Thus, as S is the least electronegative, it would be the central atom and on arranging all the valence electrons , one gets the Lewis structure of ${\text{SO}}_3^{2-}$ as: