Which of the following is the correct chemical formula for phosphorus triiodide?

• A. PI
• B. PI3
• C. P3I
• D. P2I3

Answer: (B)

Verified step by step guidance

1. Understand the naming convention: 'Phosphorus triiodide' indicates one phosphorus atom and three iodine atoms. The prefix 'tri-' means three, which applies to iodine in this case.
2. Recall that chemical formulas represent the number of atoms of each element in a compound. The element symbols are P for phosphorus and I for iodine.
3. Combine the symbols with the correct subscripts based on the name: phosphorus (P) has no prefix, so it is just one atom, and iodine (I) has the prefix 'tri-', so it has three atoms.
4. Write the formula by placing the element symbols together, with the subscript 3 after iodine to indicate three iodine atoms: \(P I_3\).
5. Verify that the formula matches the name: phosphorus triiodide corresponds to \(P I_3\), which correctly shows one phosphorus atom and three iodine atoms.