What is the name of the compound with the formula CoBr2? What is the name of the compound with the formula Ag2O? What is the name of the compound with the formula CuF2?
The correct answer and explanation is:
Correct Answers
- CoBr₂ — Cobalt(II) bromide
- Ag₂O — Silver(I) oxide
- CuF₂ — Copper(II) fluoride
Explanation (300 words):
These compounds are named using the rules for naming ionic compounds with transition metals. Transition metals often have more than one possible oxidation state. Because of this, Roman numerals are used in the name to indicate the oxidation number (charge) of the metal in the compound.
1. CoBr₂ (Cobalt(II) bromide):
Cobalt is a transition metal, and bromine is a nonmetal that forms a Br⁻ ion with a charge of –1. There are two bromide ions, giving a total negative charge of –2. To balance this, cobalt must have a +2 charge. So the compound is cobalt(II) bromide. The Roman numeral (II) shows that cobalt has a +2 oxidation state.
2. Ag₂O (Silver(I) oxide):
Silver is also a transition metal, but unlike many others, it commonly forms only one ion, Ag⁺. In Ag₂O, there are two silver ions (2 × +1 = +2) and one oxide ion, which is O²⁻. The charges balance (+2 and –2), so silver must be in the +1 oxidation state. Therefore, the compound is named silver(I) oxide. Even though silver usually forms +1 ions, the Roman numeral is included for consistency in naming transition metal compounds.
3. CuF₂ (Copper(II) fluoride):
Copper is a transition metal that can form either Cu⁺ or Cu²⁺ ions. Fluoride ions each have a charge of –1, and there are two of them in this compound (total –2). To balance this, copper must have a +2 charge. This means copper is in the +2 oxidation state in this compound. So the name is copper(II) fluoride.
These names clearly indicate the composition and charge of the metal cations in each compound. This system helps prevent confusion when metals can form multiple ions.