The correct statement about lithium sulfide is: **The atoms in lithium sulfide are held together by bonds.**
Here's why the other statements are incorrect:
1. **The chemical formula for lithium sulfide is LiS2.** - This is incorrect. The correct chemical formula for lithium sulfide is **Li2S**, indicating two lithium atoms for every one sulfur atom.
2. **A molecular model of lithium sulfide would have two spheres.** - This is misleading. While a model might show two lithium atoms and one sulfur atom, it would actually represent three spheres in total (two for lithium and one for sulfur).
3. **Both lithium and sulfur form positive ions.** - This is also incorrect. Lithium (Li) forms a positive ion (Li⁺), but sulfur (S) typically forms a negative ion (S²⁻) in ionic compounds like lithium sulfide.
Thus, the most accurate statement is about the presence of bonds holding the atoms together in lithium sulfide.