write the names for the following compounds PCl5
The correct answer and explanation is:
Correct Name for PCl₅:
Phosphorus pentachloride
Explanation (300 words):
The compound PCl₅ is a binary covalent compound, meaning it consists of two nonmetals: phosphorus (P) and chlorine (Cl). When naming covalent compounds, we follow specific rules set by the International Union of Pure and Applied Chemistry (IUPAC) to reflect the number of atoms of each element in the molecule.
Step 1: Name the first element.
The first element in the formula, phosphorus, is named using its elemental name—phosphorus.
Step 2: Name the second element.
The second element, chlorine, is named as chloride (ending changes from “-ine” to “-ide”).
Step 3: Use prefixes to show the number of atoms.
In covalent compounds, prefixes are used to indicate how many atoms of each element are present:
- Mono- = 1
- Di- = 2
- Tri- = 3
- Tetra- = 4
- Penta- = 5
- Hexa- = 6, etc.
In PCl₅:
- There is 1 phosphorus atom: we usually do not use “mono-” with the first element, so it remains simply “phosphorus.”
- There are 5 chlorine atoms, so we use the prefix “penta-“ before “chloride”, resulting in pentachloride.
Thus, the full name becomes phosphorus pentachloride.
Common Mistake:
Sometimes students mistakenly spell the name as “phosphorous” (with an extra “o”). However, “phosphorous” is an old-fashioned term used in naming acids or oxidation states, not simple covalent compounds. The correct element name is “phosphorus.”
Final Answer:
✅ Phosphorus pentachloride is the correct name for PCl₅.