Question

Write the formula for the polyatomic ion in each of the following and name each compound: a. \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) b. \(\mathrm{NH}_{4} \mathrm{Cl}\) c. \(\mathrm{K}_{3} \mathrm{PO}_{4}\) d. \(\mathrm{Cr}\left(\mathrm{NO}_{2}\right)_{2}\) e. \(\mathrm{FeSO}_{3}\)

Short answer

a. \( \mathrm{CO}_{3}^{2-} \), sodium carbonate. b. \( \mathrm{NH}_{4}^{+} \), ammonium chloride. c. \( \mathrm{PO}_{4}^{3-} \), potassium phosphate. d. \( \mathrm{NO}_{2}^{-} \), chromium(II) nitrite. e. \( \mathrm{SO}_{3}^{2-} \), iron(II) sulfite.

Step-by-step solution

Identify polyatomic ions

First, identify the polyatomic ions in each compound. Polyatomic ions are ions that consist of more than one atom.

Write the polyatomic ion for \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) and name the compound

\(\mathrm{Na}_{2} \mathrm{CO}_{3}\) contains the polyatomic ion \(\mathrm{CO}_{3}^{2-} \) which is carbonate. The compound is named sodium carbonate.

Write the polyatomic ion for \(\mathrm{NH}_{4} \mathrm{Cl}\) and name the compound

\(\mathrm{NH}_{4} \mathrm{Cl}\) contains the polyatomic ion \(\mathrm{NH}_{4}^{+} \) which is ammonium. The compound is named ammonium chloride.

Write the polyatomic ion for \(\mathrm{K}_{3} \mathrm{PO}_{4}\) and name the compound

\(\mathrm{K}_{3} \mathrm{PO}_{4}\) contains the polyatomic ion \(\mathrm{PO}_{4}^{3-} \) which is phosphate. The compound is named potassium phosphate.

Write the polyatomic ion for \(\mathrm{Cr}\left( \mathrm{NO}_{2} \right)_{2}\) and name the compound

\(\mathrm{Cr}\left( \mathrm{NO}_{2} \right)_{2}\) contains the polyatomic ion \(\mathrm{NO}_{2}^{-} \) which is nitrite. The compound is named chromium(II) nitrite.

Write the polyatomic ion for \(\mathrm{FeSO}_{3}\) and name the compound

\(\mathrm{FeSO}_{3}\) contains the polyatomic ion \(\mathrm{SO}_{3}^{2-} \) which is sulfite. The compound is named iron(II) sulfite.

Key concepts

sodium carbonate

Sodium carbonate is a compound formed from sodium ions \(\text{Na}^{+}\) and carbonate ions \(\text{CO}_{3}^{2-}\). The chemical formula for sodium carbonate is \(\text{Na}_{2}\text{CO}_{3}\).

The carbonate ion is a polyatomic ion, meaning it is made up of more than one atom. In this case, it consists of one carbon atom and three oxygen atoms.

Sodium carbonate is commonly used in cleaning products, such as laundry detergents and dishwashing liquids, due to its ability to soften water.

ammonium chloride

Ammonium chloride is formed from ammonium ions \(\text{NH}_{4}^{+}\) and chloride ions \(\text{Cl}^{-}\). Its chemical formula is \(\text{NH}_{4}\text{Cl}\).

The ammonium ion is a polyatomic ion composed of one nitrogen atom and four hydrogen atoms.
Ammonium chloride is often used in fertilizers, since it supplies nitrogen, an essential nutrient for plant growth. It is also found in certain medications and in various industrial processes.

potassium phosphate

Potassium phosphate is made from potassium ions \(\text{K}^{+}\) and phosphate ions \(\text{PO}_{4}^{3-}\), with the chemical formula \(\text{K}_{3}\text{PO}_{4}\).
Phosphate is a polyatomic ion made up of one phosphorus atom and four oxygen atoms.

Potassium phosphate is commonly used as a fertilizer ingredient due to its rich potassium and phosphorus content, which are vital for plant health. It is also used in the food industry as a buffering agent and in various industrial applications.

chromium(II) nitrite

Chromium(II) nitrite consists of chromium ions \(\text{Cr}^{2+}\) and nitrite ions \(\text{NO}_{2}^{-}\). Its chemical formula is \(\text{Cr}(\text{NO}_{2})_{2}\).

The nitrite ion is a polyatomic ion composed of one nitrogen atom and two oxygen atoms.
Chromium(II) nitrite can be used in processes that involve chromium plating or in the synthesis of other chemicals. Nitrites in general are also used as preservatives in foods to prevent bacterial growth.

iron(II) sulfite

Iron(II) sulfite is formed from iron ions \(\text{Fe}^{2+}\) and sulfite ions \(\text{SO}_{3}^{2-}\), with the chemical formula \(\text{FeSO}_{3}\).

Sulfite is a polyatomic ion made up of one sulfur atom and three oxygen atoms.

Iron(II) sulfite can be utilized in the reduction processes in the manufacturing industry and sometimes in water treatment as an oxygen scavenger. Sulfites are also used as preservatives in foods and beverages to prevent oxidation and spoilage.