Which of the following Lewis dot diagrams correctly represents the ionic compound CaCl_2?

• A. Ca^{2+} [ :Cl: ] [ :Cl: ]
• B. Ca^{2+} [ :Cl: ]^- [ :Cl: ]^-
• C. Ca^{2+} [ :Cl: ]^+ [ :Cl: ]^-
• D. Ca [ :Cl: ] [ :Cl: ]

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the nature of the compound CaCl_2. Calcium (Ca) is a metal that typically forms a Ca^{2+} cation by losing two electrons, and chlorine (Cl) is a nonmetal that forms Cl^- anions by gaining one electron each.
2. Step 2: Recognize that in an ionic compound like CaCl_2, the calcium ion will have a 2+ charge (Ca^{2+}), and each chlorine atom will have a 1- charge (Cl^-), resulting in two chloride ions to balance the charge of one calcium ion.
3. Step 3: Draw the Lewis dot structure for each chloride ion, showing the full octet of electrons around each Cl atom, and indicate the negative charge on each chloride ion as a superscript minus sign (^-).
4. Step 4: Represent the calcium ion as Ca^{2+} without any dots around it, since it has lost its valence electrons and carries a positive charge.
5. Step 5: Combine the Ca^{2+} ion with two Cl^- ions in the Lewis diagram, ensuring the charges are clearly shown and that the overall compound is electrically neutral.