 In two-dimensional close packing, hexagonal close packing achieves what fraction of space occupancy?
A~60.4%
B~52.4%
C~74.0%
D~100%
Answer & Solution
Correct answer: A. ~60.4%
**2D packings**:
- Square close packing: 52.4% (option A)
- Hexagonal close packing: 60.4% (option B)
**3D packings**:
- FCC and HCP: 74% (option C is the 3D answer, common trap)
- BCC: 68%
- Simple cubic: 52.4%
In 2D hexagonal, each circle is surrounded by 6 neighbours, which is the maximum possible for circles, giving higher efficiency than the 4-neighbour square layout.
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