What is the correct name of the binary molecular (covalent) compound $PC{l}_5$?

• A. Phosphorus chloride
• B. Phosphorus pentachloride
• C. Phosphorus(V) chloride
• D. Phosphorus chlorate

Answer: (B)

Verified step by step guidance

1. Identify the elements in the compound: P (phosphorus) and Cl (chlorine).
2. Recognize that this is a binary molecular (covalent) compound, which means it consists of two nonmetals.
3. Use prefixes to indicate the number of atoms of each element. The subscript 5 on Cl means there are five chlorine atoms.
4. The prefix for 5 is 'penta-', so the chlorine part becomes 'pentachloride'.
5. Combine the name of the first element (phosphorus) with the modified second element name to get 'phosphorus pentachloride'.