Question

Give the name of each of the following polyatomic ions. a. \(\mathrm{NH}_{4}^{+}\) b. \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) c. \(S O_{4}^{2-}\) d. \(\mathrm{HSO}_{3}^{-}\) e. \(\mathrm{ClO}_{4}^{-}\) f. \(\mathrm{IO}_{3}^{-}\)

Short answer

a. Ammonium ion \(\mathrm{NH}_{4}^{+}\) b. Hydrogen phosphate or dihydrogen phosphate ion \(\mathrm{H}_{2}\mathrm{PO}_{4}^{-}\) c. Sulfate ion \(SO_{4}^{2-}\) d. Hydrogen sulfite or bisulfite ion \(\mathrm{HSO}_{3}^{-}\) e. Perchlorate ion \(\mathrm{ClO}_{4}^{-}\) f. Iodate ion \(\mathrm{IO}_{3}^{-}\)

Step-by-step solution

a. Naming \(\mathrm{NH}_{4}^{+}\)

This ion consists of one nitrogen atom and four hydrogen atoms with a charge of +1. It is known as the ammonium ion.

b. Naming \(\mathrm{H}_{2}\mathrm{PO}_{4}^{-}\)

This ion consists of one phosphorus atom, four oxygen atoms, and two hydrogen atoms with a charge of -1. It is known as the hydrogen phosphate or dihydrogen phosphate ion.

c. Naming \(S O_{4}^{2-}\)

This ion consists of one sulfur atom and four oxygen atoms with a charge of -2. It is known as the sulfate ion.

d. Naming \(\mathrm{HSO}_{3}^{-}\)

This ion consists of one sulfur atom, three oxygen atoms, and one hydrogen atom with a charge of -1. It is known as the hydrogen sulfite or bisulfite ion.

e. Naming \(\mathrm{ClO}_{4}^{-}\)

This ion consists of one chlorine atom and four oxygen atoms with a charge of -1. It is known as the perchlorate ion.

f. Naming \(\mathrm{IO}_{3}^{-}\)

This ion consists of one iodine atom and three oxygen atoms with a charge of -1. It is known as the iodate ion.

Key concepts

Ammonium Ion

The ammonium ion, represented as \( \mathrm{NH}_{4}^{+} \), is a positively charged polyatomic ion. It is a key ion found in many chemical compounds and plays a crucial role in various biological and environmental processes.
Unlike many other polyatomic ions, ammonium carries a positive charge, making it a cation. It is formed by the addition of a proton \( (\mathrm{H}^+) \) to ammonia \( (\mathrm{NH}_{3}) \). This results in a stable configuration where nitrogen is surrounded by four hydrogen atoms.
The ammonium ion is common in fertilizers because it is an essential form of nitrogen that plants can absorb. It can also be found in numerous household and industrial cleaners.

• Ammonium is vital for plant growth.
• It appears in natural processes like the nitrogen cycle.

Understanding the ammonium ion helps in grasping its role in acid-base chemistry, where it often acts as a weak acid, readily donating a proton to water to form ammonia.

Sulfate Ion

The sulfate ion, symbolized as \( \mathrm{SO}_{4}^{2-} \), is one of the most prevalent polyatomic ions. This ion is negatively charged, specifically a dianion due to its two negative charges.
Sulfate ions are made up of one central sulfur atom surrounded by four oxygen atoms in a tetrahedral arrangement. The charges are distributed such that sulfate is a stable, typically non-reactive ion. As a result, sulfates are commonly found in a wide variety of chemical compounds.
Sulfates are hitched in nature through the sulfur cycle. They also feature prominently in industrial contexts, most notably in the manufacture of plaster, detergent, and fertilizers.

• Sulfate appears naturally in minerals and the environment.
• It's significant in biological systems for protein structure.

Additionally, understanding sulfate ions is essential in environmental science since they can affect water quality by contributing to the process of acid rain.

Perchlorate Ion

Perchlorate ion, denoted as \( \mathrm{ClO}_{4}^{-} \), is a monovalent anion, which means it carries a single negative charge. It consists of one chlorine atom surrounded by four oxygen atoms, forming a tetrahedral shape.
Perchlorate is a strong oxidizer and is commonly used in propellants, explosives, and fireworks. In these contexts, its ability to release oxygen makes it valuable for combustion reactions.

• Perchlorate is used in the aerospace and defense industries due to its energy release properties.
• It is regulated due to its persistence in the environment.

Understanding perchlorate ions is important in environmental chemistry and toxicology because they can contaminate drinking water and negatively affect human health by disrupting thyroid function.