Question

Write the chemical formula for each of the following compounds, and indicate the oxidation state of nitrogen in each: (a) sodium nitrite, (b) ammonia, (c) nitrous oxide, (d) sodium cyanide, (e) nitric acid, (f) nitrogen dioxide, (g) nitrogen, (h) boron nitride.

Short answer

(a) Sodium nitrite: NaNO2, oxidation state of N: +3. (b) Ammonia: NH3, oxidation state of N: -3. (c) Nitrous oxide: N2O, oxidation state of N: +1. (d) Sodium cyanide: NaCN, oxidation state of N: -3. (e) Nitric acid: HNO3, oxidation state of N: +5. (f) Nitrogen dioxide: NO2, oxidation state of N: +4. (g) Nitrogen gas: N2, oxidation state of N: 0. (h) Boron nitride: BN, oxidation state of N: -3.

Step-by-step solution

(a) Sodium Nitrite

To determine the chemical formula for sodium nitrite, we need to know the molecular components. Sodium (Na) is in group 1 in the periodic table, which means it has a charge of +1. Nitrite (NO2) is a polyatomic ion with a charge of -1. To balance these charges, we need one sodium atom and one nitrite ion. The chemical formula for sodium nitrite is NaNO2. The oxidation state of nitrogen in sodium nitrite is +3.

(b) Ammonia

Ammonia consists of one nitrogen (N) atom and three hydrogen (H) atoms. The chemical formula for ammonia is NH3. The oxidation state of nitrogen in ammonia is -3.

(c) Nitrous Oxide

Nitrous oxide contains two nitrogen (N) atoms and one oxygen (O) atom. The chemical formula for nitrous oxide is N2O. The oxidation state of nitrogen in nitrous oxide is +1.

(d) Sodium Cyanide

Sodium cyanide is made up of one sodium (Na) atom and one cyanide (CN) ion. The chemical formula for sodium cyanide is NaCN. Because cyanide is a polyatomic ion consisting of one carbon (C) and one nitrogen (N), the oxidation state of nitrogen in sodium cyanide is -3.

(e) Nitric Acid

Nitric acid consists of one nitrogen (N) atom, one hydrogen (H) atom, and three oxygen (O) atoms. The chemical formula for nitric acid is HNO3. The oxidation state of nitrogen in nitric acid is +5.

(f) Nitrogen Dioxide

Nitrogen dioxide is composed of one nitrogen (N) atom and two oxygen (O) atoms. The chemical formula for nitrogen dioxide is NO2. The oxidation state of nitrogen in nitrogen dioxide is +4.

(g) Nitrogen

Nitrogen gas exists as a diatomic molecule, meaning that it is composed of two nitrogen (N) atoms bonded together. The chemical formula for nitrogen gas is N2. The oxidation state of nitrogen in nitrogen gas is 0.

(h) Boron Nitride

Boron nitride is a compound made up of one boron (B) atom and one nitrogen (N) atom. The chemical formula for boron nitride is BN. The oxidation state of nitrogen in boron nitride is -3.

Key concepts

Chemical Formulas

Chemical formulas represent the proportions of atoms that make up a chemical compound. They provide a simplified representation of the molecules or ions involved in a substance. Understanding chemical formulas is crucial for expressing how elements combine to form various compounds.
For example, sodium nitrite is represented chemically as NaNO₂. Here, sodium (Na), a metallic element, combines with a nitrite ion (NO₂⁻) to form the compound. Every chemical formula provides information on the number and type of each atom in the molecule, which is crucial for understanding chemical reactions and properties.
In addition to showing the elements involved, chemical formulas can help us determine the oxidation states of elements like nitrogen in different compounds, which tells us about electron distribution and chemical stability.

Nitrogen Compounds

Nitrogen compounds are a diverse group since nitrogen can form various types of bonds and compounds thanks to its ability to assume multiple oxidation states. These states make nitrogen a versatile element in chemistry, playing a role in organic and inorganic compounds.
Take ammonia (NH₃), where nitrogen has an oxidation state of -3. This indicates it gains electrons. In contrast, nitric acid (HNO₃) presents nitrogen in a +5 oxidation state, showing it has lost electrons. The ability of nitrogen to transition between different oxidation states allows it to participate in various biochemical and industrial processes.
Key nitrogen compounds include:

• Ammonia (NH₃) - used commonly in fertilizers.
• Nitric Acid (HNO₃) - important in manufacturing fertilizers and explosives.
• Nitrogen Dioxide (NO₂) - a component of air pollution.
• Different states of nitrogen, usually encountered, range from -3 to +5, supporting its role in oxidation-reduction reactions.

Polyatomic Ions

Polyatomic ions are ions that consist of more than one atom, which remain tightly bonded to act as a single unit in chemical reactions. These ions carry a charge due to a surplus or deficit of electrons. Nitrogen is commonly found in polyatomic ions forming some essential compounds.
For example, in the nitrite ion (NO₂⁻), nitrogen exhibits an oxidation state of +3. This ion frequently pairs with alkali metals like sodium to form compounds such as sodium nitrite (NaNO₂). Being well-acquainted with polyatomic ions is vital for understanding various chemical equations and reactions.
Some widely recognized nitrogen-containing polyatomic ions include:

• Nitrate ( O₃⁻) - found in fertilizers and explosives.
• Nitrite (NO₂⁻) - used in food preservation and various industries.
• Cyanide (CN⁻) - a lethal ion commonly used in mining and synthetic chemistry.

These ions play significant roles in industrial and environmental chemistry.