Classification Of Solids

In solid state, PCl₅ forms an ionic compound. The phosphorus atom (P) has an empty 3d orbital and can expand its octet to form a compound with more than four bonds. In PCl₅, it forms five bonds with chlorine atoms, but in the solid state, it forms an ionic compound by losing one electron to form a cation [PCl₄]⁺ and gaining an electron to form an anion [PCl₆]^-.

Why is option (C) correct?

• PCl₅ forms an ionic compound in the solid state.
• The cation formed is [PCl₄]⁺ and the anion formed is [PCl₆]^-.

Why are the other options incorrect?

• Option (A): PCl₅ does not have an octahedral structure in the solid state.
• Option (B): The ions are reversed. The correct ions are [PCl₄]⁺ and [PCl₆]^-.
• Option (D): PCl₅ does not form a covalent solid in the form of P₂Cl₁₀.

Conclusion: The correct answer is (C) Ionic solid with [PCl₄]⁺ and [PCl₆]^- because PCl₅ forms an ionic compound in the solid state with these specific ions.