When do you use a Roman numeral in an ionic name?

When the metal can have more than one charge (like iron or copper), the numeral shows which charge it has in that compound.

Do ionic compounds use prefixes like "di" or "tri"?

No. Prefixes are used only for molecular compounds; ionic names are set by the ion charges.

Grade 11 · Chemistry

Naming ionic compounds and hydrates

Why it matters

Naming from a formula (Stock system) and naming hydrates.

Core20m readingPrerequisite: Ions and constructing ionic formulas

How do you name ionic compounds?

Short answer

To name an ionic compound, name the cation (metal) first, then the anion (non-metal) with its ending changed to -ide, as in sodium chloride. Polyatomic ions keep their own names. When a metal forms more than one charge, a Roman numeral shows which one, as in iron(III) oxide. No prefixes are used for ionic compounds.

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Frequently asked questions

When do you use a Roman numeral in an ionic name?: When the metal can have more than one charge (like iron or copper), the numeral shows which charge it has in that compound.
Do ionic compounds use prefixes like "di" or "tri"?: No. Prefixes are used only for molecular compounds; ionic names are set by the ion charges.

How do you name ionic compounds?

Related topics

Frequently asked questions