Question

What is the formula of lanthanoids with sulfur?

• A. \( \text{La}_2\text{S}_3 \)
• B. \( \text{LaS}_2 \)
• C. \( \text{La}_3\text{S}_4 \)
• D. \( \text{La}_4\text{S}_3 \)

Hint:

In lanthanide compounds with sulfur, lanthanum typically forms a +3 oxidation state, and sulfur forms a -2 oxidation state to balance the charges.

Answer 1

The Correct Option is A

Lanthanoids (or lanthanides) are typically metals, and their compounds with sulfur form sulfides. The most common lanthanide sulfides have the general formula \( \text{La}_2\text{S}_3 \), where lanthanum is in the +3 oxidation state.

1. Step 1: Oxidation state of lanthanum. Lanthanum typically forms a +3 oxidation state, and sulfur typically forms a -2 oxidation state.

2. Step 2: Balance the charges. For a neutral compound, two \( \text{La}^{3+} \) ions are needed to balance three \( \text{S}^{2-} \) ions, giving the formula \( \text{La}_2\text{S}_3 \). Thus, the correct formula for lanthanum sulfide is \( \text{La}_2\text{S}_3 \).