Identify the crystal structure of anhydrous $\mathrm{AlCl_3}$ in solid state

In the crystalline state, anhydrous $\mathrm{AlCl_3}$ does not exist as discrete $\mathrm{AlCl_3}$ units. Instead, it forms a layered structure.

Coordination around $\mathrm{Al}$

In this solid structure, each $\mathrm{Al}$ atom is surrounded by 6 chloride ions arranged octahedrally.

Therefore, the coordination number of $\mathrm{Al}$ is: $6$

Final answer

$\boxed{6}$

Comparison with stored correct answer

The stored correct answer is $6$, which matches the derived answer.