What is the correct name for the molecular compound PCl_3?

• A. Phosphorus(III) chloride
• B. Phosphoric trichloride
• C. Phosphorus chloride
• D. Phosphorus trichloride

Answer: (D)

Verified step by step guidance

1. Identify the elements in the compound: PCl_3 consists of phosphorus (P) and chlorine (Cl).
2. Determine the number of atoms of each element: There is 1 phosphorus atom and 3 chlorine atoms.
3. Recall the naming rules for molecular (covalent) compounds: Use prefixes to indicate the number of atoms (mono-, di-, tri-, etc.) for the second element, and the first element's name remains unchanged without the prefix 'mono-' if there is only one atom.
4. Name the first element as 'phosphorus' since there is only one atom of phosphorus and no prefix is needed for the first element.
5. Name the second element with the appropriate prefix and change its ending to '-ide': since there are 3 chlorine atoms, use the prefix 'tri-' and change chlorine to 'chloride', resulting in 'trichloride'. Combine to get 'phosphorus trichloride'.