The correct name for K2S is potassium sulfate
A dipotassium sulfate
B potassium bisulfide
C potassium sulfide
D potassium disulfide
The correct answer and explanation is :
The correct name for K₂S is Potassium sulfide. Therefore, the correct answer is:
C. Potassium sulfide.
Explanation:
To understand the correct name of K₂S, let’s break down the compound.
- K₂S is made up of two elements: potassium (K) and sulfur (S).
- Potassium (K) is an alkali metal from Group 1 of the periodic table. It forms a cation with a +1 charge, denoted as K⁺.
- Sulfur (S) is a nonmetal from Group 16. When it bonds with metals, it typically forms an anion with a -2 charge, written as S²⁻.
Naming Ionic Compounds:
The general rule for naming ionic compounds is to name the cation first (in this case, potassium) and then the anion (sulfide in this case). For a simple ionic compound like K₂S, you follow these steps:
- Cation Naming: The potassium ion is K⁺. When potassium forms an ionic compound, it retains its name “potassium.”
- Anion Naming: The sulfide ion is formed by sulfur, which has gained two electrons to form S²⁻. The name of the anion is derived from the element’s root name, sulfur, and adding the suffix “-ide” to it. Hence, it becomes sulfide.
The compound K₂S consists of two potassium ions (K⁺) and one sulfide ion (S²⁻). So, the name of the compound is potassium sulfide.
Why Not the Other Options?
- A. Dipotassium sulfate: This name would apply to K₂SO₄ (potassium sulfate), which is a different compound. Sulfate (SO₄²⁻) involves a polyatomic ion, while sulfide (S²⁻) is a simple ion.
- B. Potassium bisulfide: This name would apply to a compound with a sulfide ion and a hydrogen ion (e.g., KHS), but this is not K₂S.
- D. Potassium disulfide: This name would refer to a compound with two sulfur atoms, such as K₂S₂, which is not the case here.
Thus, C. Potassium sulfide is the correct answer.