Problem 84 - Chemistry: An Atoms-Focused Approach

Question

What is the oxidation number of nitrogen in each of the following species? (a) elemental nitrogen \(\left(\mathrm{N}_{2}\right) ;\) (b) hydrazine \(\left(\mathrm{N}_{2} \mathrm{H}_{4}\right) ;(\mathrm{c})\) ammonium ion \(\left(\mathrm{NH}_{4}^{+}\right)\)

Step-by-Step Solution

Answer

Answer: The oxidation numbers of nitrogen in the given species are: (a) Elemental nitrogen (N₂): 0 (b) Hydrazine (N₂H₄): -2 (c) Ammonium ion (NH₄⁺): -3

Step 1: Understand the concept of oxidation numbers

Oxidation numbers are assigned to elements in a chemical species to help keep track of electron transfer during chemical reactions. They represent the charge that an atom would have if all bonding pairs of electrons were assigned to the more electronegative atom. Here are some rules to assign oxidation numbers: 1. The oxidation number of an element in its elemental state is always zero. 2. The oxidation number of a monatomic ion is equal to its charge. 3. In a neutral molecule, the sum of oxidation numbers of all its elements is zero. 4. In an ion, the sum of oxidation numbers of all its elements is equal to the charge of the ion.

Step 2: Determine the oxidation number of nitrogen in elemental nitrogen (N₂)

Using Rule 1, the oxidation number of nitrogen in elemental nitrogen (N₂) is zero since it is in its elemental state. Hence, the oxidation number of nitrogen in N₂ is: Oxidation number of N in N₂ = 0

Step 3: Determine the oxidation number of nitrogen in hydrazine (N₂H₄)

First, we assign oxidation numbers using Rule 2 to the hydrogen atoms in hydrazine, each hydrogen atom has an oxidation number of +1. The molecule N₂H₄ is neutral, so using Rule 3, we calculate the oxidation number of nitrogen as follows: Sum of oxidation numbers = (2 × Oxidation number of N) + (4 × (+1)) = 0 Solving this equation for the oxidation number of N, we get: Oxidation number of N in N₂H₄ = -2

Step 4: Determine the oxidation number of nitrogen in ammonium ion (NH₄⁺)

First, we assign oxidation numbers using Rule 2 to the hydrogen atoms in the ammonium ion, each hydrogen atom has an oxidation number of +1. The ammonium ion has a charge of +1, so using Rule 4, we calculate the oxidation number of nitrogen as follows: Sum of oxidation numbers = Oxidation number of N + (4 × (+1)) = +1 Solving this equation for the oxidation number of N, we get: Oxidation number of N in NH₄⁺ = -3 To summarize, the oxidation numbers of nitrogen in the given species are: (a) Elemental nitrogen (N₂): 0 (b) Hydrazine (N₂H₄): -2 (c) Ammonium ion (NH₄⁺): -3

Key Concepts

Oxidation States

Oxidation states, sometimes referred to as oxidation numbers, are crucial in understanding chemical reactions. They help us track the movement of electrons, offering insights into how atoms bond and react with one another. Each element is assigned a unique oxidation state based on specific rules.

• The oxidation state of an atom in its elemental form is always zero. For example, in the molecule nitrogen gas (\( \mathrm{N}_2\) ), each nitrogen has an oxidation state of 0.
• For monatomic ions, the oxidation state equals the ion's charge. For instance, Na⁺ has an oxidation state of +1.
• In compounds, the more electronegative atom takes on a negative oxidation state by gaining shared electrons.

These principles are essential. They allow us to determine how electrons are distributed and how they change during reactions. Mastery of oxidation states will help you balance chemical equations and predict reaction products. This is vital for grasping the intricate details of chemical processes.

Chemical Reactions

Chemical reactions occur when substances interact, transforming into new products. Reactions depend heavily on the exchange of electrons and consequently on the oxidation states of the elements involved. When one substance loses electrons, it undergoes oxidation. Meanwhile, gaining electrons results in reduction. This interplay is known as redox reactions, split into two main halves: oxidation and reduction.

• Oxidation involves the increase of oxidation states, meaning electrons are lost.
• Reduction involves the decrease of oxidation states, indicating electrons are gained.

The changes in oxidation states help determine which substances are oxidized and which are reduced. An understanding of these shifts allows chemists to predict how reactants convert into products. It also plays a role in large-scale applications such as energy storage in batteries and industrial synthesis. By understanding chemical reactions through oxidation states, you gain deeper insights into the dynamic world of chemistry.

Electron Transfer

Electron transfer is a fundamental aspect of chemical reactions, especially in redox reactions where electron movement is charted. In this context, oxidation states offer a window into the behavior of electrons. When atoms form bonds, they share electrons which can lead to changes in their oxidation states. When the sharing is unequal, the more electronegative atom attracts the electrons closer, taking a negative oxidation state, while the other atom becomes more positive.

• In oxidation reactions, electrons are passed from one atom to another, resulting in an increase in oxidation state.
• This contrasts with reduction reactions, where an atom receives electrons, thereby lowering its oxidation state.

In reactions involving ions, understanding electron transfer is crucial as ions tend to combine by mutual electron exchange to reach stable configurations. Electron transfer is not only vital in understanding chemical changes but is also the backbone of many technologies, including biological processes like respiration and photosynthesis. It is this transfer that powers metabolism and supports life as we know it.

Ammonium Ion

The ammonium ion, \( \mathrm{NH}_4^+ \), is a vital polyatomic ion in chemistry. Understanding its structure and the oxidation state of nitrogen within it is crucial. In the ammonium ion, nitrogen is bonded to four hydrogen atoms, creating a positive charge. This occurs due to nitrogen completely sharing its electrons with four hydrogens, leaving the ion with a net positive charge.

• Each hydrogen atom, typically manifesting an oxidation number of +1, partially absorbs electrons from nitrogen.
• The nitrogen, because of these interactions, carries an oxidation number of -3 to balance out the +1 charge of the ion.

The ammonium ion is significant in both organic and inorganic chemistry. It forms the basis for important compounds like ammonium nitrate, a crucial fertilizer, and is a central component in many biochemical pathways. By comprehending the electron sharing and oxidation states within the ammonium ion, chemists can make informed predictions about the behavior and reactivity of related compounds.