Question

If the oxidation number of nitrogen in a certain molecule changes from +3 to -2 during a reaction, is the nitrogen oxidized or reduced? How many electrons are gained or lost by the nitrogen atom?

Short answer

Nitrogen is reduced, gaining 5 electrons.

Step-by-step solution

Identify the Change in Oxidation Number

First, determine the change in oxidation number for nitrogen. It goes from +3 to -2 during the reaction.

Definition of Oxidation and Reduction

Oxidation is the loss of electrons and an increase in oxidation number, while reduction is the gain of electrons and a decrease in oxidation number.

Determine the Process Experienced by Nitrogen

Since the oxidation number of nitrogen decreases from +3 to -2, nitrogen gains electrons.

Calculate the Number of Electrons Gained

The change in oxidation number is from +3 to -2, which is a decrease of 5 units. This means that nitrogen gains 5 electrons.

Key concepts

Oxidation Numbers

Understanding oxidation numbers is crucial when studying chemical reactions. Essentially, an oxidation number is a bookkeeping tool used to keep track of electrons in atoms during a chemical reaction. It can be thought of as a hypothetical charge that an atom would have if all of its bonds to atoms of different elements were completely ionic.

For instance, in the exercise question, we're looking at the change in oxidation number for nitrogen. If nitrogen starts with an oxidation number of +3 and then changes to -2, we can determine that there's a movement in the electrons around nitrogen. It is important to realize that whole numbers are assigned to oxidation states, which simplifies the understanding of electron transfer.

Redox Reactions

Redox reactions, or oxidation-reduction reactions, are processes that involve the transfer of electrons between two species. These reactions are fundamental to numerous chemical processes, including combustion, rusting, photosynthesis, and cellular respiration. In a redox reaction, we find both oxidation and reduction processes occurring simultaneously.

In the exercise, we observe a change in oxidation number for nitrogen as it participates in a redox reaction. An easy way to remember redox processes is the mnemonic 'LEO the lion says GER': Loss of Electrons is Oxidation, Gain of Electrons is Reduction. Determining which substance is oxidized and which is reduced is essential to understanding the overall redox reaction.

Electron Transfer

Electron transfer is the movement of electrons from one atom, molecule, or ion to another, which is the hallmark of redox reactions. Electrons carry energy, so their movement from one species to another is not only a transfer of charge but also a transfer of energy.

The textbook exercise details a decline in oxidation number for nitrogen. This decrease implies that nitrogen gains electrons—five, to be exact. Since oxidation involves losing electrons and reduction involves gaining electrons, we can thus infer that the nitrogen in this scenario is undergoing reduction. Monitoring electron transfer allows chemists to predict the behavior of substances in various chemical reactions.

Chemical Reactions

Chemical reactions involve the rearrangement of atoms to form new substances, and these transformations are underpinned by the breaking and forming of chemical bonds. Recognizing changes in oxidation numbers can provide insights into the types of chemical reactions occurring. For example, when we see a change in the oxidation numbers like in the case of nitrogen from +3 to -2, we can conclude that a chemical reaction has taken place.

In our exercise, by observing the oxidation numbers, we recognize the nitrogen atom's role in the reaction and can deduce that it has undergone a chemical transformation by gaining electrons. This simple yet powerful concept helps us predict the outcomes of chemical reactions and understand the properties of the resulting substances.