Question

Assign the oxidation state for nitrogen in each of the following. a. \(\mathrm{Li}_{3} \mathrm{~N} \quad\) f. \(\mathrm{NO}_{2}\) b. \(\mathrm{NH}_{3} \quad\) g. \(\mathrm{NO}_{2}^{-}\) c. \(\mathrm{N}_{2} \mathrm{H}_{4} \quad\) h. \(\mathrm{NO}_{3}\) d. NO i. \(\mathrm{N}_{2}\) e. \(\mathrm{N}_{3} \mathrm{O}\)

Short answer

The oxidation states of nitrogen in the given compounds are as follows: a. Li₃N: N = -3 b. NH₃: N = -3 c. N₂H₄: N = -2 d. NO: N = +2 e. N₃O: N = +2/3 f. NO₂: N = +4 g. NO₂⁻: N = +3 h. NO₃: N = +6 i. N₂: N = 0

Step-by-step solution

Assign oxidation states for each compound

Use the rules for assigning oxidation states to find the oxidation state of nitrogen in each compound. a. Li₃N

Rule 1 (Alkali metals)

Alkali metals have an oxidation state of +1. Each Li atom has an oxidation state of +1.

Rule 3 (Sum of oxidation states)

The sum of oxidation states in a neutral compound should be 0. There are three Li atoms, resulting in a total of +3. To balance the compound, N must have an oxidation state of -3. b. NH₃

Rule 2 (Hydrogen)

Hydrogen has an oxidation state of +1 when bonded to non-metal elements. There are three H atoms, resulting in a total of +3.

Rule 3 (Sum of oxidation states)

N must have an oxidation state of -3 to balance the compound. c. N₂H₄

Rule 2 (Hydrogen)

There are four H atoms, resulting in a total of +4.

Rule 3 (Sum of oxidation states)

Since the compound is neutral and there are two N atoms, each N must have an oxidation state of -2. d. NO

Rule 4 (Oxygen)

Oxygen has an oxidation state of -2.

Rule 3 (Sum of oxidation states)

To balance the compound, N must have an oxidation state of +2. e. N₃O

Rule 4 (Oxygen)

Oxygen has an oxidation state of -2.

Rule 3 (Sum of oxidation states)

Since there are three N atoms, each N must have an oxidation state of +2/3 to balance the compound. f. NO₂

Rule 4 (Oxygen)

There are two O atoms, resulting in a total of -4.

Rule 3 (Sum of oxidation states)

N must have an oxidation state of +4 to balance the compound. g. NO₂⁻

Rule 4 (Oxygen)

There are two O atoms, resulting in a total of -4.

Rule 3 (Sum of oxidation states)

Since the compound has a charge of -1, N must have an oxidation state of +3 to balance the compound. h. NO₃

Rule 4 (Oxygen)

There are three O atoms, resulting in a total of -6.

Rule 3 (Sum of oxidation states)

N must have an oxidation state of +6 to balance the compound. i. N₂

Rule 5 (Same element)

Diatomic molecules of the same element have an oxidation state of 0. N₂ has two N atoms, each with an oxidation state of 0.

Key concepts

Nitrogen Compounds

Nitrogen compounds are diverse and found in various chemical forms. They are used in many applications, from fertilizers to explosives. In chemistry, understanding the oxidation states of nitrogen in these compounds helps determine their reactivity and properties.

• Li₃N: A compound where lithium is bound to nitrogen.
• NH₃: Known as ammonia, a common nitrogen compound.
• N₂H₄: Hydrazine, used as a rocket propellant.
• NO: Nitric oxide, involved in various biological processes.
• N₃O: Azide oxide, less common but still important in chemistry.
• NO₂: Nitrogen dioxide, a significant air pollutant.
• NO₂⁻: Nitrite, found in various biological systems.
• NO₃: Nitrate, commonly found in fertilizers.
• N₂: Molecular nitrogen, making up most of Earth's atmosphere.

Recognizing the structure and composition of these compounds is crucial for assigning the correct oxidation states.

Rules for Assigning Oxidation States

Assigning oxidation states involves following specific rules that simplify the electron accounting in compounds. These rules allow chemists to understand how electrons are distributed in molecules.

• Alkali Metals: Always have an oxidation state of +1.
• Hydrogen: Typically, +1 when bonded to non-metals.
• Oxygen: Generally, -2 in compounds.
• Sum of Oxidation States: The total must equal the overall charge of the compound.
• Same Element: In diatomic molecules like N₂, the oxidation state is 0.

These guidelines are essential for systematically determining unknown oxidation states in chemical compounds.

Oxidation State Calculations

Calculating oxidation states requires applying the rules to balance the charges in a compound. Let's explore some calculations:

Example: Li₃N

Lithium, being an alkali metal, has +1. With three lithium atoms, the total is +3, so nitrogen must be -3 to balance.

Example: NH₃

With hydrogen at +1, the three hydrogens total +3. Therefore, nitrogen is -3 to create a neutral molecule.

Example: NO

Oxygen is -2; thus, nitrogen must be +2 for a balanced equation.
Consistently applying these calculations ensures accurate representation of each element's oxidation state.

Redox Chemistry

Redox chemistry involves the transfer of electrons between species, altering their oxidation states. These reactions are central to many biochemical and industrial processes.

• Reduction: Gain of electrons, decreasing the oxidation state.
• Oxidation: Loss of electrons, increasing the oxidation state.
• Balancing Redox Reactions: Requires equalizing both the mass and charge.

Understanding redox chemistry helps in analyzing processes like cellular respiration or metal corrosion. The shift in oxidation states during these reactions provides insight into the pathways and mechanisms involved.