Question

Predict the formula of a compound formed by aluminum and sulfur.

• A. $A{l}_2{S}_2$
• B. $A{l}_3{S}_2$
• C. $A{l}_2{S}_3$
• D. $AlS$

Answer 1

Answer: (C)

$A{l}_2{S}_3$

$Al-3e^{-}\to A{l}^{3+},S+2e^{-}\to S^{2-}$

$Al$ loses three electrons to form $A{l}^{3+}$ ion. $S$ gains two electrons to form $S^{2-}$ ion.

Two $A{l}^{3+}$ ions combine with three $S^{2-}$ ions to form $A{l}_2{S}_3$.

Note: In a neutral molecule, the total charge on cations is numerically equal to the total charge on anions.