Which of the following is the correct chemical formula for cobalt(III) fluoride?

• A. CoF2
• B. CoF3
• C. Co3F2
• D. Co2F3

Answer: (B)

Verified step by step guidance

1. Identify the oxidation state of cobalt in cobalt(III) fluoride. The Roman numeral III indicates that cobalt has a +3 charge, so Co is Co^{3+}.
2. Determine the charge of the fluoride ion. Fluoride (F) is a halide ion with a charge of -1, so F is F^{-}.
3. Balance the total positive and negative charges to form a neutral compound. Since cobalt is +3 and fluoride is -1, you need three fluoride ions to balance one cobalt ion.
4. Write the chemical formula by combining one Co^{3+} ion with three F^{-} ions, resulting in CoF_3.
5. Verify that the formula is electrically neutral: the total positive charge (+3) from cobalt equals the total negative charge (3 × -1 = -3) from fluoride ions.