Question

Complete these structures by adding bonds and lone pairs as necessary. Then, determine the nitrogen-to-oxygen bond order in each ion.

Answer 1

Concepts and reason

• In Chemistry, Lewis structure represents the number of electrons present around each atom of molecule as a bonding electrons as well as non-bonding electrons. For molecule, the number of bonds and lone pairs can be added following the octet rule.

• Bond order of the molecule represents the number of bonds present between the atoms. Bond order is the measurement of the bond strength of a molecule. An increase in the bond order shows the increase in the bond strength.

Fundamentals

Bond order is calculated using the following formula:

${\rm{Bond}}\,{\rm{order}}\,{\rm{ = }}\,\frac{{{\rm{Total number of electron pairs in N - O bond}}}}{{{\rm{Total number of}}\,{\rm{N - O bond groups}}}}$

The structure of ${\rm{NO}}_3^ -$ molecule is given below:

From the given structure of ${\rm{NO}}_3^ -$ molecule,

The total number of electron pairs in ${\rm{N}} - {\rm{O}}$ bond = 4 electron pairs.

The total number of ${\rm{N}} - {\rm{O}}$ bond groups = 3bonds (1 double bond, 2 single bonds).

The bond order is calculated below:

$\begin{array}{c}\\{\rm{Bond}}\,{\rm{order}}\,{\rm{ = }}\,\frac{{{\rm{Total number of electron pairs in N - O bond}}}}{{{\rm{Total number of}}\,{\rm{N - O bond groups}}}}\\\\{\rm{Bond}}\,{\rm{order}}\,{\rm{ = }}\,\frac{4}{3}\\\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{ = }}\,\,1.3.\\\end{array}$

Therefore, nitrogen-to-oxygen bond order of the ${\rm{NO}}_3^ -$ molecule = 1.33.

The structure of ${\rm{NO}}_3^ -$ molecule is given below:

From the given structure of ${\rm{NO}}_2^ -$ molecule,

The total number of electron pairs in ${\rm{N}} - {\rm{O}}$ bond = 3 electron pairs.

The total number of ${\rm{N}} - {\rm{O}}$ bond groups = 2 bonds (1 double bond, 1 single bond).

The bond order is calculated below:

$\begin{array}{c}\\{\rm{Bond}}\,{\rm{order}}\,{\rm{ = }}\,\frac{{{\rm{Total number of electron pairs in N - O bond}}}}{{{\rm{Total number of}}\,{\rm{N - O bond groups}}}}\\\\{\rm{Bond}}\,{\rm{order}}\,{\rm{ = }}\,\frac{3}{2}\\\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{ = }}\,\,1.5\\\end{array}$

Therefore, nitrogen-to-oxygen bond order of the ${\rm{NO}}_2^ -$ molecule = 1.5

The structure of ${\rm{NO}}_3^ -$ molecule is given below:

From the given structure of ${\rm{NO}}_2^ +$ molecule,

The total number of electron pairs in ${\rm{N}} - {\rm{O}}$ bond = 4 electron pairs

The total number of ${\rm{N}} - {\rm{O}}$ bond groups = 2 bonds(2 double bonds)

The bond order is calculated below:

$\begin{array}{c}\\{\rm{Bond}}\,{\rm{order}}\,{\rm{ = }}\,\frac{{{\rm{Total number of electron pairs in N - O bond}}}}{{{\rm{Total number of}}\,{\rm{N - O bond groups}}}}\\\\{\rm{Bond}}\,{\rm{order}}\,{\rm{ = }}\,\frac{4}{2}\\\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\rm{ = }}\,\,2.\\\end{array}$

Therefore, nitrogen-to-oxygen bond order in ${\rm{NO}}_2^ -$ molecule = 2

Ans:

The nitrogen-to-oxygen bond order is given below:

The nitrogen-to-oxygen bond order is given below:

The nitrogen-to-oxygen bond order is given below: