Question

1. which ion could bond with a calcium ion (ca²⁺) to form a neutral ionic compound? a. cl⁻ b. mg²⁺ c. s²⁻ d. no₃⁻

Explanation:

Step1: Recall ionic - compound charge - balance rule

In a neutral ionic compound, the sum of the charges of the cations and anions must be zero. Calcium ion has a charge of +2 ($Ca^{2 + }$).

Step2: Analyze each option

• Option A: Chloride ion ($Cl^{-}$) has a charge of - 1. Two $Cl^{-}$ ions are needed to balance the +2 charge of $Ca^{2+}$ to form $CaCl_{2}$.
• Option B: Magnesium ion ($Mg^{2+}$) has a charge of +2. Two positive - charged ions cannot form a neutral compound.
• Option C: Sulfide ion ($S^{2 - }$) has a charge of - 2. One $S^{2 - }$ ion can balance the +2 charge of $Ca^{2+}$ to form $CaS$.
• Option D: Nitrate ion ($NO_{3}^{-}$) has a charge of - 1. Two $NO_{3}^{-}$ ions are needed to balance the +2 charge of $Ca^{2+}$ to form $Ca(NO_{3})_{2}$.

Answer:

C. $S^{2 - }$