The correct statement about lithium sulfide is:
- **The atoms in lithium sulfide are held together by bonds.**
Here's a brief clarification of the other statements:
1. **A molecular model of lithium sulfide would have two spheres.** - This statement is misleading; a proper molecular model would not necessarily just consist of two spheres since it also includes sulfur.
2. **Both lithium and sulfur form positive ions.** - This is incorrect. Lithium (Li) forms a positive ion (Li⁺), while sulfur (S) typically forms a negative ion (S²⁻).
3. **The chemical formula for lithium sulfide is LiS?** - This is incorrect; the correct chemical formula for lithium sulfide is Li₂S, indicating two lithium atoms for every one sulfur atom.