Question

what is the formula for the compound that can form between lithium and sulfur?
○ li₂s
○ lis
○ li₃s₂
○ li₂so₄

Explanation:

To determine the formula of the compound formed between lithium (Li) and sulfur (S), we analyze their oxidation states. Lithium is an alkali metal with an oxidation state of +1 (\( \text{Li}^+ \)). Sulfur, in binary ionic compounds with metals, typically has an oxidation state of -2 (\( \text{S}^{2-} \)). To balance the charges, we need two \( \text{Li}^+ \) ions to balance one \( \text{S}^{2-} \) ion (since \( 2(+1) + (-2) = 0 \)). This gives the formula \( \text{Li}_2\text{S} \).

• \( \text{LiS} \) is incorrect because the charges (+1 and -2) are not balanced.
• \( \text{Li}_3\text{S}_2 \) does not follow the typical oxidation states for Li and S in a binary compound.
• \( \text{Li}_2\text{SO}_4 \) contains the sulfate ion (\( \text{SO}_4^{2-} \)), but the question asks for a compound between Li and S (not involving sulfate), so this is incorrect.

Answer:

A. \( \text{Li}_2\text{S} \)