Question

Which of the following nitrogen oxides are odd-electron molecules? (a) \(\mathrm{NO} ;\) (b) \(\mathrm{NO}_{2} ;\) (c) \(\mathrm{NO}_{3} ;\) (d) \(\mathrm{N}_{2} \mathrm{O}_{4} ;\) (e) \(\mathrm{N}_{2} \mathrm{O}_{5}.\)

Short answer

Answer: NO, NO2, and NO3 are odd-electron molecules.

Step-by-step solution

Determine the number of electrons in each molecule

We will begin by determining the number of electrons in each nitrogen oxide molecule. 1. NO: This molecule has one nitrogen (N) atom and one oxygen (O) atom. Nitrogen has 7 valence electrons, and oxygen has 6 valence electrons. Therefore, NO has a total of 7 + 6 = 13 electrons. 2. NO2: This molecule has one nitrogen (N) atom and two oxygen (O) atoms. Thus, NO2 has a total of 7 + 2 * 6 = 19 electrons. 3. NO3: This molecule has one nitrogen (N) atom and three oxygen (O) atoms. Thus, NO3 has a total of 7 + 3 * 6 = 25 electrons. 4. N2O4: This molecule has two nitrogen (N) atoms and four oxygen (O) atoms. Thus, N2O4 has a total of 2 * 7 + 4 * 6 = 38 electrons. 5. N2O5: This molecule has two nitrogen (N) atoms and five oxygen (O) atoms. Thus, N2O5 has a total of 2 * 7 + 5 * 6 = 44 electrons.

Identify odd-electron molecules

Now, we will identify the odd-electron molecules by looking at the total number of electrons in each molecule. A molecule is considered an odd-electron molecule if it has an odd total number of electrons. 1. NO: 13 electrons (odd) 2. NO2: 19 electrons (odd) 3. NO3: 25 electrons (odd) 4. N2O4: 38 electrons (even) 5. N2O5: 44 electrons (even) So, the nitrogen oxides that are odd-electron molecules are NO, NO2, and NO3.

Key concepts

Nitrogen Oxides

Nitrogen oxides are a group of compounds that consist of nitrogen and oxygen. These chemicals are significant in both environmental and industrial contexts. They are often formed during the combustion of fossil fuels, which is why they are crucial in discussions about air pollution and climate change.
These compounds include various oxides of nitrogen, such as nitric oxide (NO), nitrogen dioxide (NO2), and others like nitrous oxide (N2O), but in this context, we're focusing on those outlined in the exercise.

• They participate actively in atmospheric reactions that can lead to the formation of ozone and other pollutants.
• Nitrogen oxides can also act as oxidizing agents in chemical reactions.
• Some of these oxides, particularly NO and NO2, are known for their roles in the formation of smog and acid rain.

This blend of chemical and environmental roles makes understanding their properties and behaviors, such as electron configuration and molecular structures, essential.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial in determining how an element will react chemically. For nitrogen, this involves five valence electrons, while oxygen has six. Understanding how these electrons can be shared or exchanged in chemical reactions provides a basis for predicting molecule behavior.

• Knowing the number of valence electrons helps predict the types of bonds an atom can form.
• It provides insight into the molecule's stability, reactivity, and type of bonds (ionic, covalent).
• These electrons are involved in forming chemical bonds and subsequent structures.

In our exercise, identifying the valence electrons in nitrogen and oxygen helps us determine how they come together to form different nitrogen oxides and if any are odd-electron molecules.

Electron Count

The electron count of a molecule indicates the total number of electrons in its structure, which involves summing up the electrons associated with each atom in the molecule. For nitrogen oxides, this involves adding up the electrons for each nitrogen and oxygen atom present in the structure.
This is a crucial step in understanding which molecules may have odd electrons, as these are often more reactive due to unpaired electrons. Here's how electron counting is used:

• Calculate the total number of valence electrons from all atoms in the molecule.
• Assess whether the total count is odd or even to establish if it is an odd-electron molecule.
• Identify unpaired electrons, which influence potential molecular stability and reactivity.

By performing this electron count, we identified NO, NO2, and NO3 as odd-electron molecules in the exercise.

Molecular Structure

Molecular structure refers to the arrangement of atoms within a molecule. In nitrogen oxides, this structure defines how the nitrogen and oxygen atoms are bonded together. Understanding the structure can offer insights into physical properties and chemical reactivity.
Molecular structures are usually depicted in diagrams showing bonds between atoms, representing single, double, or triple bonds. Here’s why these structures matter:

• Molecular geometry affects the molecule's chemical properties and interactions with other molecules.
• Structures determine how electrons are distributed and can help identify areas of potential reactivity.
• They play a role in understanding the stability of a molecule, especially those involving odd numbers of electrons.

For instance, in nitrogen oxides like NO and NO2, which have unpaired electrons, their molecular structures can indicate where reactions might occur, impacting their role in various environmental processes.