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🧪 Chemistry  ·  Solid State  ·  NEET & JEE

What is the coordination number in a face-centred cubic (FCC) structure?

Answer: 12.

  • A 4
  • B 6
  • C 8
  • D 12

Correct answer: D. 12

Explanation: In FCC/ccp, each atom is surrounded by 12 nearest neighbours.

Cubic Unit Cells: Atom PositionsSimple CubicCN=6, 52.4% packedBody-Centred (BCC)CN=8, 68% packedFace-Centred (FCC)CN=12, 74% packed (densest)Corner atoms (shared by 8 cells) shown lighter; body/face-centre atoms shown solid

The three cubic unit cells: Simple Cubic has atoms only at corners; Body-Centred adds one atom at the centre; Face-Centred adds one atom at the centre of each of the 6 faces, giving the highest packing efficiency.

Concept context

Explore the ordered world of crystalline solids: unit cells, packing, defects, and how structure determines electrical and magnetic properties.

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