* Magnesium chloride (MgCl₂) is a solid at room temperature. This is because it forms an ionic lattice structure where positively charged magnesium ions (Mg²⁺) are strongly attracted to negatively charged chloride ions (Cl⁻). These strong electrostatic forces hold the ions together in a rigid, crystalline structure.

* Chlorine (Cl₂) is a gas at room temperature. This is due to the weak intermolecular forces (van der Waals forces) between chlorine molecules. These forces are not strong enough to hold the molecules together in a liquid or solid state at room temperature.

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