What ions make up the ionic compound Fe2(SO3)3? Cation: Fe2+ Anion: (SO3)3-
The Correct Answer and Explanation is:
Correct Answer:
- Cation: Fe³⁺
- Anion: SO₃²⁻
Explanation
The ionic compound Fe₂(SO₃)₃ is composed of two types of ions: a cation (positively charged ion) and an anion (negatively charged ion). To determine what these ions are, we must analyze the chemical formula.
First, let’s identify the cation. The element iron (Fe) is a transition metal, which means it can form more than one type of ion with different charges. In this compound, the formula shows two iron (Fe) atoms. The full formula includes three sulfite (SO₃) groups. Each sulfite ion has a charge of 2−, so the total negative charge contributed by three sulfite ions is 3 × (−2) = −6.
For the compound to be electrically neutral, the total positive charge from the iron ions must balance the −6 charge from the sulfite ions. Since there are two Fe atoms, and the total positive charge must be +6, each Fe ion must have a charge of +3. Therefore, the cation is Fe³⁺, also known as iron(III).
Now, let’s identify the anion. The polyatomic ion SO₃ is known as sulfite, and it carries a charge of 2−, written as SO₃²⁻. This is a common polyatomic anion made of one sulfur atom and three oxygen atoms.
So, the ionic compound Fe₂(SO₃)₃ consists of:
- Two Fe³⁺ ions (each with a +3 charge, totaling +6)
- Three SO₃²⁻ ions (each with a −2 charge, totaling −6)
The charges cancel out, resulting in a neutral compound. It’s important to distinguish Fe³⁺ from Fe²⁺, which would form a different compound entirely, and to correctly write the sulfite ion as SO₃²⁻, not (SO₃)₃⁻, which is incorrect.
