Chapter 1, Problem 1.40P

Assign formal charges to each $\text{N}$ and $\text{O}$ atom in the given molecules. All lone pairs have been drawn in.

a. b. c. d.

Interpretation Introduction

(a)

Interpretation: The formal charge to each $\text{N}$ and $\text{O}$ atom in the given molecule is to be assigned.

Concept introduction:

The formal charge on an atom is calculated by the formula,

$\text{Formal charge}=\text{Valence electrons}-\left[\text{Nonbonding electrons}+\frac{1}{2}\left(\text{Bonding electrons}\right)\right]$

Answer to Problem 1.40P

In the given molecule, the formal charge on nitrogen atom is $-\text{1}$ as shown below.

Explanation of Solution

The given molecule is,

Figure 1

The formal charge on an atom is calculated by the formula,

$\text{Formal charge}=\text{Valence electrons}-\left[\text{Nonbonding electrons}+\frac{1}{2}\left(\text{Bonding electrons}\right)\right]$

For the nitrogen atom,

$\begin{array}{rll}\text{Number}\text{of}\text{valence}\text{electrons}& =& \text{5}\\ \text{Number}\text{of}\text{bonding}\text{electrons}& =& 4\\ \text{Number}\text{of}\text{nonbonding}\text{electrons}& =& 4\end{array}$

Substitute these values in above equation to calculate the formal charge on nitrogen atom.

$\begin{array}{rll}\text{Formal charge}& =& \text{5}-\left[\text{4}+\frac{1}{2}\times \text{4}\right]\\ & =& 5-6\\ & =& -1\end{array}$

Thus, in the given molecule, the formal charge on nitrogen atom is $-\text{1}$ as shown below.

Figure 2

Conclusion

In the given molecule, the formal charge on nitrogen atom is $-\text{1}$.

Interpretation Introduction

(b)

Interpretation: The formal charge to each $\text{N}$ and $\text{O}$ atom in the given molecules is to be assigned.

Concept introduction: The formal charge on an atom is calculated by the formula,

$\text{Formal charge}=\text{Valence electrons}-\left[\text{Nonbonding electrons}+\frac{1}{2}\left(\text{Bonding electrons}\right)\right]$

Answer to Problem 1.40P

The formal charge to each $\text{N}$ atom in the given molecule is shown as,

Explanation of Solution

The given molecule is,

Figure 3

Here, a, b, and c are used to indicate nitrogen atoms.

The formal charge on an atom is calculated by the formula,

$\text{Formal charge}=\text{Valence electrons}-\left[\text{Nonbonding electrons}+\frac{1}{2}\left(\text{Bonding electrons}\right)\right]$

For the nitrogen atom, $\text{N}\left(\text{a}\right)$.

$\begin{array}{rll}\text{Number}\text{of}\text{valence}\text{electrons}& =& \text{5}\\ \text{Number}\text{of}\text{bonding}\text{electrons}& =& 4\\ \text{Number}\text{of}\text{nonbonding}\text{electrons}& =& 4\end{array}$

Substitute these values in the above equation to calculate the formal charge on $\text{N}\left(\text{a}\right)$.

$\begin{array}{rll}\text{Formal charge}& =& \text{5}-\left[\text{4}+\frac{1}{2}\times \text{4}\right]\\ & =& 5-6\\ & =& -1\end{array}$

In the given molecule, bond pairs and lone pairs in $\text{N}\left(\text{a}\right)$ is same as in $\text{N}\left(\text{c}\right)$.

Thus, the formal charge on $\text{N}\left(\text{a}\right)$ and $\text{N}\left(\text{c}\right)$ is $-\text{1}$.

For the nitrogen atom, $\text{N}\left(\text{b}\right)$.

$\begin{array}{rll}\text{Number}\text{of}\text{valence}\text{electrons}& =& \text{5}\\ \text{Number}\text{of}\text{bonding}\text{electrons}& =& 8\\ \text{Number}\text{of}\text{nonbonding}\text{electrons}& =& 0\end{array}$

Substitute these values in the above equation to calculate the formal charge on $\text{N}\left(\text{b}\right)$.

$\begin{array}{rll}\text{Formal charge}& =& \text{5}-\left[\text{0}+\frac{1}{2}\times \text{8}\right]\\ & =& 5-4\\ & =& +1\end{array}$

Thus, the formal charge on $\text{N}\left(\text{b}\right)$ is $+1$.

Hence, the formal charge to each $\text{N}$ atom in the given molecule is,

Figure 4

Conclusion

In the given molecule, the formal charge on nitrogen atom of both $\text{a}$ and $\text{c}$ is $-\text{1}$, and the formal charge on nitrogen atom of $\text{b}$ is $+1$.

Interpretation Introduction

(c)

Interpretation: The formal charge to each $\text{N}$ and $\text{O}$ atom in the given molecules is to be assigned.

Concept introduction: The formal charge on an atom is calculated by the formula,

$\text{Formal charge}=\text{Valence electrons}-\left[\text{Nonbonding electrons}+\frac{1}{2}\left(\text{Bonding electrons}\right)\right]$

Answer to Problem 1.40P

In the given molecule, the formal charge on oxygen atom is $+\text{1}$ as shown below.

Explanation of Solution

The given species is,

Figure 5

The formal charge on an atom is calculated by the formula,

$\text{Formal charge}=\text{Valence electrons}-\left[\text{Nonbonding electrons}+\frac{1}{2}\left(\text{Bonding electrons}\right)\right]$

For the oxygen atom,

$\begin{array}{rll}\text{Number}\text{of}\text{valence}\text{electrons}& =& \text{6}\\ \text{Number}\text{of}\text{bonding}\text{electrons}& =& 6\\ \text{Number}\text{of}\text{nonbonding}\text{electrons}& =& 2\end{array}$

Substitute these values in above equation, to calculate the formal charge on oxygen atom.

$\begin{array}{rll}\text{Formal charge}& =& \text{6}-\left[\text{2}+\frac{1}{2}\times \text{6}\right]\\ & =& 6-5\\ & =& +1\end{array}$

Thus, in the given molecule, the formal charge on oxygen atom is $+\text{1}$ as shown below.

Figure 6

Conclusion

In the given molecule, the formal charge on oxygen atom is $+\text{1}$.

Interpretation Introduction

(d)

Interpretation: The formal charge to each $\text{N}$ and $\text{O}$ atom in the given molecules is to be assigned.

Concept introduction: The formal charge on an atom is calculated by the formula,

$\text{Formal charge}=\text{Valence electrons}-\left[\text{Nonbonding electrons}+\frac{1}{2}\left(\text{Bonding electrons}\right)\right]$

Answer to Problem 1.40P

In the given molecule, the formal charge on both nitrogen and oxygen atom is zero as shown below.

Explanation of Solution

The given species is,

Figure 7

The formal charge on an atom is calculated by the formula,

$\text{Formal charge}=\text{Valence electrons}-\left[\text{Nonbonding electrons}+\frac{1}{2}\left(\text{Bonding electrons}\right)\right]$

For the oxygen atom,

$\begin{array}{rll}\text{Number}\text{of}\text{valence}\text{electrons}& =& \text{6}\\ \text{Number}\text{of}\text{bonding}\text{electrons}& =& 4\\ \text{Number}\text{of}\text{nonbonding}\text{electrons}& =& 4\end{array}$

Substitute these values in above equation, to calculate the formal charge on oxygen atom.

$\begin{array}{rll}\text{Formal charge}& =& \text{6}-\left[\text{4}+\frac{1}{2}\times \text{4}\right]\\ & =& 6-6\\ & =& 0\end{array}$

For the nitrogen atom,

$\begin{array}{rll}\text{Number}\text{of}\text{valence}\text{electrons}& =& \text{5}\\ \text{Number}\text{of}\text{bonding}\text{electrons}& =& 6\\ \text{Number}\text{of}\text{nonbonding}\text{electrons}& =& 2\end{array}$

Substitute these values in above equation, to calculate the formal charge on nitrogen atom.

$\begin{array}{rll}\text{Formal charge}& =& \text{5}-\left[\text{2}+\frac{1}{2}\times \text{6}\right]\\ & =& 5-5\\ & =& 0\end{array}$

Thus, in the given molecule, the formal charge on both nitrogen and oxygen is zero as shown below.

Figure 8

Conclusion

In the given molecule, the formal charge on both nitrogen and oxygen is zero.