Problem 125 - A Complete Resource Book in Chemistry for JEE Main

Question

The nitrogen oxide(s) that contains(s) \(\mathrm{N}-\mathrm{N}\) bond(s) is are [IIT 2009] (a) \(\mathrm{N}_{2} \mathrm{O}\) (b) \(\mathrm{N}_{2} \mathrm{O}_{3}\) (c) \(\mathrm{N}_{2} \mathrm{O}_{4}\) (d) \(\mathrm{N}_{2} \mathrm{O}_{5}\)

Step-by-Step Solution

Answer

\( \mathrm{N}_2\mathrm{O} \), \( \mathrm{N}_2\mathrm{O}_3 \), and \( \mathrm{N}_2\mathrm{O}_4 \) contain \( \mathrm{N} - \mathrm{N} \) bonds.

Step 1: Analyze the Structures

To identify which nitrogen oxide contains an \( \mathrm{N} - \mathrm{N} \) bond, we need to consider the molecular structures of the given nitrogen oxides: \( \mathrm{N}_{2}\mathrm{O} \), \( \mathrm{N}_{2}\mathrm{O}_3 \), \( \mathrm{N}_{2}\mathrm{O}_4 \), and \( \mathrm{N}_{2}\mathrm{O}_5 \).

Step 2: Review \( \mathrm{N}_{2}\mathrm{O} \)

The structural formula of \( \mathrm{N}_{2}\mathrm{O} \) is \( \mathrm{N} \equiv \mathrm{N} - \mathrm{O} \). This indicates the presence of an \( \mathrm{N} - \mathrm{N} \) bond.

Step 3: Review \( \mathrm{N}_{2}\mathrm{O}_3 \)

The structure of \( \mathrm{N}_{2}\mathrm{O}_3 \) is \( \mathrm{(O=N-O-N=O)} \). It has an \( \mathrm{N} - \mathrm{N} \) bond as well.

Step 4: Review \( \mathrm{N}_{2}\mathrm{O}_4 \)

The structure of \( \mathrm{N}_{2}\mathrm{O}_4 \) is \( \mathrm{O_2N-NO_2} \) or \( \mathrm{O=N-O-N=O} \). This compound also contains an \( \mathrm{N} - \mathrm{N} \) bond.

Step 5: Review \( \mathrm{N}_{2}\mathrm{O}_5 \)

In \( \mathrm{N}_{2}\mathrm{O}_5 \), the structure is \( \mathrm{O_2N-O-NO_2} \). This structure contains an \( \mathrm{N} - \mathrm{O} - \mathrm{N} \) sequence but no direct \( \mathrm{N} - \mathrm{N} \) bond.

Step 6: Conclude

After analyzing the structures, we observe that \( \mathrm{N}_{2}\mathrm{O} \), \( \mathrm{N}_{2}\mathrm{O}_3 \), and \( \mathrm{N}_{2}\mathrm{O}_4 \) have \( \mathrm{N} - \mathrm{N} \) bonds.

Key Concepts

Chemical Bonding

Chemical bonding is the process that holds atoms together in molecules and crystals. There are various types of chemical bonds, such as ionic, covalent, and metallic, but covalent bonding is crucial when discussing nitrogen oxides. In covalent bonds, atoms share pairs of electrons. This sharing allows each atom to achieve a stable electron configuration.
In the context of nitrogen oxides:

• The atoms involved are nitrogen and oxygen.
• Nitrogen usually forms stable covalent bonds because it needs three additional electrons to complete its valence shell.
• Oxygen, needing two electrons to fill its shell, also readily forms covalent bonds.

In compounds like \( ext{N}_2 ext{O}, ext{N}_2 ext{O}_3, ext{and N}_2 ext{O}_4\), there's an important presence of a nitrogen-nitrogen bond. Such bonds result from overlapping orbitals between nitrogen atoms, sharing electrons to make a stable linkage.

Molecular Structure

Understanding the molecular structure of nitrogen oxides is key to identifying specific bonds, like nitrogen-nitrogen bonds. Molecular structure refers to how atoms are arranged in a molecule and the geometry they form.
For nitrogen oxides:

• \( \text{N}_2\text{O} \): has a linear arrangement with a triple bond between nitrogen atoms \( \text{N}\equiv\text{N} - \text{O} \).
• \( \text{N}_2\text{O}_3 \): features a sequence where nitrogen and oxygen atoms create a bent structure, but crucially, there's \( \text{N} - \text{N}\) in-between.
• \( \text{N}_2\text{O}_4 \): takes a planar structure. Notably, it includes \( \text{N} - \text{N} \) linkage in the layout \( \text{O}_2\text{N} - \text{NO}_2 \).
• \( \text{N}_2\text{O}_5 \): characterized by no direct \( \text{N} - \text{N} \) bond but rather includes an \( \text{N} - \text{O} - \text{N} \) sequence.

These different configurations influence molecules' chemical behaviors and reactions.

Nitrogen-Nitrogen Bond

The nitrogen-nitrogen bond is a specific type of covalent bond where two nitrogen atoms are directly linked. This bond can vary in strength and length depending on the number of shared electron pairs:

• Single bond \( \text{N} - \text{N} \)
• Double bond \( \text{N} = \text{N} \)
• Triple bond \( \text{N} \equiv \text{N} \)

Nitrogen atoms can form triple bonds like in \( \text{N}_2\text{O} \), indicating shared six electrons, making it very strong and stable. This disposition affects the molecule's reactivity and overall properties:

• Triple bonds are less reactive than double or single bonds due to their strength.
• The bond type influences the molecule's ability to dissociate, impacting its behavior during reactions.

A strong \( \text{N} \equiv \text{N} \) bond is responsible for the inert nature of molecular nitrogen \( \text{N}_2 \) in the atmosphere, but within nitrogen oxides, such bonds significantly impact how these oxides function chemically.