Answer :

Negative and positive ions alternate in the ionic crystals. For instance, the melting point of calcium fluoride (CaF) is 1418 °C. Therefore, four  Cl⁻ ions are in a single unit cell.

What is Crystalline Solid?

The description of crystalline solid states that it is a substance whose atoms or even subatomic particles are organized in a highly structured form. Atomic nuclei in metallic crystals are surrounded by a "sea" of delocalized electrons.

Molecules of many types make up molecular crystals. Atoms that are covalently bound to one another make up covalent network crystals. Jewelry is crafted with diamond. Quartz is used to create things like watches and wall clocks. One unit cell of the sodium chloride lattice includes eight ions in total, four of which are Na+ ions and four of which are  Cl⁻ ions.

Therefore, four  Cl⁻ ions are in a single unit cell.

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