Final answer:
The formula for phosphorus triiodide is PI3, as indicated by the prefix 'tri-' which shows there are three iodine atoms present.
Step-by-step explanation:
The formula of phosphorus triiodide is PI3. In naming binary non-metal compounds, the prefixes are used to denote the number of atoms present. The prefix 'tri-' indicates that there are three atoms of iodine combined with one atom of phosphorus. Therefore, the correct answer is option e. PI3.
To clarify, this matches the way other similar compounds are named and formulated, such as:
- Phosphorus pentachloride - PCl5
- Dinitrogen monoxide - N2O
- Carbon tetrachloride - CCl4
Understanding the naming conventions is key to determining correct chemical formulas in Chemistry.