Which compound is solid

Account for the following: PCI_5 behaves as an ionic compound is solid state.

Ionic compounds are solids and hard because :

Why are ionic compounds solid and hard at room temperature?

Why ionic compound are solid at room temoerature?

Name a covalent compound which is solid at room temperature and wriite down its electron-dot structure.

Which silicon compound is used in machinary (with moving parts) in a manner similar to the use of an allotrops a covalent network solid and a molecular solid?

Which silicon compound is used in machinary (with moving parts) in a manner similar to the use of an allotrops a covalent network solid and a molecular solid?

How will check the purity of a pure chemical compound in the solid state ?