Question

part a
cao is named calcium oxide and not calcium(ii) oxide. why?
○ because calcium is among those metals that forms an ion with the same charge in all of its compounds.
○ because ionic compounds never require the charge of the ion to be included in the name.
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Explanation:

To determine why CaO is named calcium oxide (not calcium(I) oxide), we analyze the options:

• Option 1: "Because calcium is among those metals that forms an ion with the same charge in all of its compounds." Calcium is an alkali - earth metal (Group 2), so it always forms a \(Ca^{2+}\) ion in its compounds. When a metal has only one common ionic charge, we don't use a Roman numeral in the name of its ionic compounds.
• Option 2: "Because ionic compounds never require the charge of the ion to be included in the name." This is incorrect. For metals with multiple ionic charges (e.g., Fe, which can be \(Fe^{2+}\) or \(Fe^{3+}\)), we do include the charge (as a Roman numeral) in the compound name (e.g., iron(II) oxide, iron(III) oxide).

So the correct option is the first one.

Answer:

Because calcium is among those metals that forms an ion with the same charge in all of its compounds.