Chapter 7, Problem 7.105QP

Draw Lewis structures and give the other information requested for the following molecules: (a) BF₃, Shape: planar or nonplanar? (b) ClO₃⁻ Shape: planar or nonplanar? (c) HCN. Polar or nonpolar? (d) OF₂. Polar or nonpolar? (c) NO₂. Estimate the ONO bond angle.

Interpretation Introduction

Interpretation: The Lewis structures of the given molecules should be drawn. To identify whether ${\text{BF}}_{\text{3}}$ and ${\text{ClO}}_{\text{3}}{}^{-}$ is planar and whether $\text{HCN}$ and ${\text{OF}}_{\text{2}}$ are polar. Also the bond angle of ${\text{NO}}_{\text{2}}$ should be found out.

Concept Introduction:

• Molecular geometry is the spatial arrangement of atoms in a molecule. It is the three dimensional arrangement of bonded atoms. Many chemical, physical and even biological properties depend on molecular geometry.
• Bond angle measured that made between two nearby bonds. The angles between two adjacent bonds are known as bond angle.
• Using VSEPR theory and Lewis structure, the exact geometry of a molecule can be obtained.
• In VSEPR, the geometry of the molecule is explained based on minimizing electrostatic repulsion between the molecules’ valence electrons around a central atom
• Lewis structures is also known as Lewis dot structures which represents the bonding between atoms of a molecule and the lone pairs of electronsthat may exist in the molecule.
• While formation of a bond, there is a chance that electronegativity between the atoms are high. It tends to make the bond partially ionic and are called polar molecule. When the electronegativity between two atoms is similar, sharing of electron in the bond is equal and is called nonpolar molecules.

Answer to Problem 7.105QP

 is the Lewis structure of ${\text{BF}}_{\text{3}}$ and is planar

Explanation of Solution

Lewis structure of ${\text{BF}}_{\text{3}}$ is drawn below.

Here boron is taken as the central atom with three terminal fluorine atoms since electronegativity of boron is less than fluorine. The total number of valence electrons is found to be 24, where each of the fluorine atoms contributes 6 electrons whereas boron contributes 3 electrons.

The 18 electrons getting after reducing two electrons for each bond from the total valence electron are distributed on terminal fluorine atom to complete the octet. After the distribution of electrons on the terminal atoms, each fluorine atoms gets 3 pairs of electrons.

Here the central atom boron atom does not have any lone pair of electrons whereas the terminal fluorine atoms have 3 pairs of electron. It is a ${\text{AB}}_3$ type molecule and has three electron domains. Since there is no lone pair on the central atom, to minimize the repulsion, they form a trigonal planar geometry.

Interpretation Introduction

Interpretation: The Lewis structures of the given molecules should be drawn. To identify whether ${\text{BF}}_{\text{3}}$ and ${\text{ClO}}_{\text{3}}{}^{-}$ is planar and whether $\text{HCN}$ and ${\text{OF}}_{\text{2}}$ are polar. Also the bond angle of ${\text{NO}}_{\text{2}}$ should be found out.

Concept Introduction:

• Molecular geometry is the spatial arrangement of atoms in a molecule. It is the three dimensional arrangement of bonded atoms. Many chemical, physical and even biological properties depend on molecular geometry.
• Bond angle measured that made between two nearby bonds. The angles between two adjacent bonds are known as bond angle.
• Using VSEPR theory and Lewis structure, the exact geometry of a molecule can be obtained.
• In VSEPR, the geometry of the molecule is explained based on minimizing electrostatic repulsion between the molecules’ valence electrons around a central atom
• Lewis structures is also known as Lewis dot structures which represents the bonding between atoms of a molecule and the lone pairs of electronsthat may exist in the molecule.
• While formation of a bond, there is a chance that electronegativity between the atoms are high. It tends to make the bond partially ionic and are called polar molecule. When the electronegativity between two atoms is similar, sharing of electron in the bond is equal and is called nonpolar molecules.

Answer to Problem 7.105QP

is the Lewis structure of ${\text{ClO}}_{\text{3}}{}^{-}$ and is nonplanar.

Explanation of Solution

Lewis structure of ${\text{ClO}}_{\text{3}}{}^{-}$ is drawn below.

Here chlorine is taken as the central atom with three terminal oxygen atoms. The total number of valence electrons is found to be 25 where each of the oxygen atoms contributes 6 electrons whereas chlorine contributes 5 electrons. The charge of the whole molecule is -1 making the total number of valence electrons 26.

The 20 electrons getting after reducing two electrons for each bond from the total valence electron are distributed on terminal oxygen atom to complete the octet. Remaining 2 electrons were distributed on central phosphorous atom. Since the atoms do not obey the octet rule two double bonds are made between chlorine and oxygen atoms.

In the case of ${\text{ClO}}_{\text{3}}{}^{-}$, the central atom chlorine atom have a lone pair of electron whereas the terminal oxygen atoms have 3 pairs of electron and is a ${\text{AB}}_3$ with one lone pair of electron type molecule. It has four electron domains. Since there is one lone pair on the central atom, to minimize the repulsion, they form trigonal pyramid geometry. So ${\text{ClO}}_{\text{3}}{}^{-}$ is a nonplanar molecule.

Interpretation Introduction

Interpretation: The Lewis structures of the given molecules should be drawn. To identify whether ${\text{BF}}_{\text{3}}$ and ${\text{ClO}}_{\text{3}}{}^{-}$ is planar and whether $\text{HCN}$ and ${\text{OF}}_{\text{2}}$ are polar. Also the bond angle of ${\text{NO}}_{\text{2}}$ should be found out.

Concept Introduction:

• Molecular geometry is the spatial arrangement of atoms in a molecule. It is the three dimensional arrangement of bonded atoms. Many chemical, physical and even biological properties depend on molecular geometry.
• Bond angle measured that made between two nearby bonds. The angles between two adjacent bonds are known as bond angle.
• Using VSEPR theory and Lewis structure, the exact geometry of a molecule can be obtained.
• In VSEPR, the geometry of the molecule is explained based on minimizing electrostatic repulsion between the molecules’ valence electrons around a central atom
• Lewis structures is also known as Lewis dot structures which represents the bonding between atoms of a molecule and the lone pairs of electronsthat may exist in the molecule.
• While formation of a bond, there is a chance that electronegativity between the atoms are high. It tends to make the bond partially ionic and are called polar molecule. When the electronegativity between two atoms is similar, sharing of electron in the bond is equal and is called nonpolar molecules.

Answer to Problem 7.105QP

is the Lewis structure of $\text{HCN}$ and is polar.

Explanation of Solution

Lewis structure of $\text{HCN}$ is drawn below.

Here carbon is taken as the central atom with onenitrogen and one hydrogen atom in the terminal position since electronegativity of carbon is less. The total number of valence electrons is found to be 10, where each of the nitrogen atoms contributes 5 electrons whereas carbon contributes 4 electrons whereas hydrogen atom contributes only one electron.

The 6 electrons getting after reducing two electrons for each bond from the total valence electron are distributed on terminal nitrogen atom to complete the octet. Since the atoms do not obey the octet rule a triple bond is made between carbon and nitrogen atom.

In $\text{HCN}$ both $\text{H}-\text{C}$ and $\text{H}-\text{N}$ bond is polar due the difference in electronegativity of carbon with hydrogen and nitrogen. Here nitrogen atom has the highest electronegativity so two vectors are generated in both the bonds and thus a total dipole moment is formed making the molecule polar.

Interpretation Introduction

Interpretation: The Lewis structures of the given molecules should be drawn. To identify whether ${\text{BF}}_{\text{3}}$ and ${\text{ClO}}_{\text{3}}{}^{-}$ is planar and whether $\text{HCN}$ and ${\text{OF}}_{\text{2}}$ are polar. Also the bond angle of ${\text{NO}}_{\text{2}}$ should be found out.

Concept Introduction:

• Molecular geometry is the spatial arrangement of atoms in a molecule. It is the three dimensional arrangement of bonded atoms. Many chemical, physical and even biological properties depend on molecular geometry.
• Bond angle measured that made between two nearby bonds. The angles between two adjacent bonds are known as bond angle.
• Using VSEPR theory and Lewis structure, the exact geometry of a molecule can be obtained.
• In VSEPR, the geometry of the molecule is explained based on minimizing electrostatic repulsion between the molecules’ valence electrons around a central atom
• Lewis structures is also known as Lewis dot structures which represents the bonding between atoms of a molecule and the lone pairs of electronsthat may exist in the molecule.
• While formation of a bond, there is a chance that electronegativity between the atoms are high. It tends to make the bond partially ionic and are called polar molecule. When the electronegativity between two atoms is similar, sharing of electron in the bond is equal and is called nonpolar molecules.

Answer to Problem 7.105QP

Answer

is the Lewis structure of ${\text{OF}}_{\text{2}}$ and is polar.

Explanation of Solution

Lewis structure of ${\text{OF}}_{\text{2}}$ is drawn below.

Here oxygenis taken as the central atom with two terminal fluorine atoms since electronegativity of oxygen is less than fluorine. The total number of valence electrons is found to be 20, where each of the fluorine atoms contributes 7 electrons whereas oxygen contributes 6 electrons.

The 16 electrons getting after reducing two electrons for each bond from the total valence electron are distributed on silicon atom to complete the octet. After the distribution of electrons on the terminal atoms, each fluorine atoms gets 3 pairs of electrons. The remaining 4 electrons are distributed to the oxygen atom.

The central atom has two lone pairs thus it has four electron domains so it have bent geometry. Due to the difference in the electronegativity the bonds are polar. But due to the presence of lone pair on the central atom, the molecule is not symmetrical. The dipole vectors do not cancel each other thus having a total dipole moment on the molecule. So it is a polar molecule.

Interpretation Introduction

Interpretation: The Lewis structures of the given molecules should be drawn. To identify whether ${\text{BF}}_{\text{3}}$ and ${\text{ClO}}_{\text{3}}{}^{-}$ is planar and whether $\text{HCN}$ and ${\text{OF}}_{\text{2}}$ are polar. Also the bond angle of ${\text{NO}}_{\text{2}}$ should be found out.

Concept Introduction:

• Molecular geometry is the spatial arrangement of atoms in a molecule. It is the three dimensional arrangement of bonded atoms. Many chemical, physical and even biological properties depend on molecular geometry.
• Bond angle measured that made between two nearby bonds. The angles between two adjacent bonds are known as bond angle.
• Using VSEPR theory and Lewis structure, the exact geometry of a molecule can be obtained.
• In VSEPR, the geometry of the molecule is explained based on minimizing electrostatic repulsion between the molecules’ valence electrons around a central atom
• Lewis structures is also known as Lewis dot structures which represents the bonding between atoms of a molecule and the lone pairs of electronsthat may exist in the molecule.
• While formation of a bond, there is a chance that electronegativity between the atoms are high. It tends to make the bond partially ionic and are called polar molecule. When the electronegativity between two atoms is similar, sharing of electron in the bond is equal and is called nonpolar molecules.

Answer to Problem 7.105QP

 is the Lewis structure of ${\text{NO}}_{\text{2}}$ and its bond angle is ${\text{135}}^{\text{0}}$

Explanation of Solution

Lewis structure of ${\text{NO}}_{\text{2}}$ is drawn below.

Here nitrogen is taken as the central atom with two terminal oxygen atoms since electronegativity of oxygen is less than fluorine. The total number of valence electrons is found to be 20, where each of the fluorine atoms contributes 7 electrons whereas oxygen contributes 6 electrons.

The 12 electrons getting after reducing two electrons for each bond from the total valence electron are distributed on terminal oxygen atom to complete the octet. The remaining one electron is distributed to the nitrogen atom. Since the atoms do not obey the octet rule a double bond is made between one of the oxygen and nitrogen atom.

${\text{NO}}_{\text{2}}$ has odd number of electrons where the central nitrogen atom has one lone electron. Usually a $\text{O}-\text{N}-\text{O}$ bond have bond angle about ${\text{120}}^{\text{0}}$ where there is a lone pair of electron on the central atom but here there is only one. So the repulsive force experience by the atom is less so the bond angle formed should be more than ${\text{120}}^{\text{0}}$. Experimentally it is found that ${\text{NO}}_{\text{2}}$ forms a bond angle about of ${\text{135}}^{\text{0}}$