Question

Explain why uncharged atoms or molecules never crystallise in a simple cubic structure.

Answer 1

1. Low Packing Efficiency: Simple cubic structures have only 52.4% packing efficiency, meaning nearly half of the space is empty. This loose packing makes the structure unstable for uncharged atoms.
2. Low Coordination Number: The coordination number in a simple cubic structure is 6, which is too low to provide sufficient intermolecular forces for uncharged atoms.
3. Weak Interactions: Uncharged atoms rely on weak van der Waals forces, which are not strong enough to stabilize the loose packing of a simple cubic structure.
4. Preference for Dense Structures: Uncharged atoms or molecules generally prefer more efficiently packed structures like fcc or hcp, which have higher coordination numbers and greater stability.