Which of the following best describes the Lewis dot structure for the ionic compound Li2S?

• A. All atoms retain their valence electrons, and no ions are formed; the structure shows neutral Li and S atoms.
• B. Each Li atom shares one electron with the S atom, forming two covalent bonds between Li and S.
• C. Each Li atom loses one electron to form Li+, and the S atom gains two electrons to form S2−; the structure shows two Li+ ions and one S2− ion with a complete octet.
• D. The S atom loses two electrons to form S2+, and each Li atom gains one electron to form Li−.

Answer: (C)

Verified step by step guidance

1. Identify the types of elements involved: lithium (Li) is a metal and sulfur (S) is a nonmetal, which suggests the compound is ionic rather than covalent.
2. Recall that in ionic compounds, metals tend to lose electrons to form positive ions (cations), and nonmetals tend to gain electrons to form negative ions (anions).
3. Determine the charges on the ions: lithium typically loses one electron to form Li⁺, and sulfur typically gains two electrons to form S²⁻ to achieve a full octet.
4. Write the formula showing the ratio of ions needed to balance the overall charge: since each S²⁻ ion requires two Li⁺ ions to balance the charge, the formula is Li₂S.
5. Represent the Lewis structure by showing two Li⁺ ions (without valence electrons) and one S²⁻ ion with a complete octet of electrons around it, indicating the transfer of electrons rather than sharing.