What is the name of K2S?
A) Potassiumsulphide
B) potassium disulphide
C) potassium (II) sulphide
D) potassium sulphide
The correct answer and explanation is :
The correct answer is D) Potassium sulphide.
Explanation:
K2S is the chemical formula for potassium sulphide, a compound made up of potassium (K) and sulphur (S). To understand this, let’s break down the formula:
- Potassium (K): Potassium is an alkali metal from Group 1 of the periodic table. It typically forms ions with a +1 charge (K⁺). This is because potassium atoms tend to lose one electron to achieve a stable electron configuration similar to the nearest noble gas (argon).
- Sulphur (S): Sulphur is a non-metal element found in Group 16 of the periodic table. Sulphur typically forms ions with a -2 charge (S²⁻) because it gains two electrons to complete its valence shell, achieving a stable configuration.
To form a neutral compound, the charges on the ions must balance out. Potassium has a +1 charge, and sulphur has a -2 charge. Since two potassium ions (K⁺) are needed to balance the -2 charge from one sulphide ion (S²⁻), the chemical formula for potassium sulphide is K₂S.
The options given:
- A) Potassiumsulphide: This is an incorrect name because it lacks proper formatting and clarity between the two elements (potassium and sulphide).
- B) Potassium disulphide: This name suggests the presence of two sulphur atoms, which is not correct for K₂S, which contains only one sulphur atom.
- C) Potassium (II) sulphide: This is incorrect because potassium always forms a +1 ion, so the oxidation state of potassium in K₂S is +1, not +2. Therefore, the term “(II)” is not applicable here.
- D) Potassium sulphide: This is the correct name, as it properly reflects the composition of the compound with one sulphide ion (S²⁻) and two potassium ions (K⁺).
In summary, K₂S is named potassium sulphide, reflecting its composition of two potassium ions and one sulphide ion.