Statement I: Only metallic, never ionic or covalent substances, form crystals exhibiting the maximum coordination number of twelve among like-sized atoms. Statement II: In metallic crystals, the force

Question

Statement I: Only metallic, never ionic or covalent substances, form crystals exhibiting the maximum coordination number of twelve among like-sized atoms. Statement II: In metallic crystals, the forces are non-directional and hence arrangement of atoms frequently corresponds to the closest packing of spheres.

Prashant Kotian · Accepted Answer

Correct answer: A. Statement I is correct: only metallic crystals form HCP or CCP lattices with CN = 12 among like-sized atoms because the metallic bond is non-directional. Ionic and covalent bonds are highly directional or require charge balances which limit the coordination. Statement II is correct and is the direct explanation of Statement I.

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