Which of the following best represents the Lewis dot structure for the ions in potassium sulfide (K2S)?

• A. Each K atom gains one electron to form K^-, and the S atom loses two electrons to form S^{2+}.
• B. Each K atom loses one electron to form K^+, and the S atom gains two electrons to form S^{2-}, resulting in [K^+] [K^+] [S^{2-}] with S having 8 valence electrons.
• C. The S atom has 6 valence electrons and each K atom has 8 valence electrons in the final structure.
• D. Each K atom shares one electron with S, forming two K–S single bonds.

Answer: (B)

Verified step by step guidance

1. Identify the correct charges on the ions in potassium sulfide (K2S). Potassium (K) is an alkali metal that typically loses one electron to form K^+, and sulfur (S) typically gains two electrons to form S^{2-}.
2. Determine the electron transfer: each K atom loses one electron, so two K atoms lose a total of two electrons, which are gained by the sulfur atom, resulting in K^+ and S^{2-} ions.
3. Draw the Lewis dot structures for the ions separately: K^+ ions have no valence electrons shown because they have lost their single valence electron, while S^{2-} has gained two electrons, completing its octet with 8 valence electrons.
4. Understand that in ionic compounds like K2S, electrons are transferred rather than shared, so there are no covalent bonds (no shared electron pairs) between K and S atoms; instead, the structure consists of K^+ and S^{2-} ions arranged in a lattice.
5. Conclude that the correct Lewis structure representation shows two K^+ ions without dots (since they lost their valence electrons) and one S^{2-} ion with 8 valence electrons (dots) around it, reflecting the full octet.