What is the co-ordination number of each sphere in
(i) Hexagonal close packed structure.
(ii) Cubic close packed structure.
(iii) Body centred cubic packed structure.

Explanation

To determine the coordination number of each sphere in the given structures, we will analyze each structure step by step.

### Step 1: Hexagonal Close Packed Structure (HCP)
- In a hexagonal close packed structure, each sphere is surrounded by 12 other spheres.
- This arrangement allows for the maximum packing efficiency and is characteristic of HCP.
- **Coordination Number for HCP = 12**

### Step 2: Cubic Close Packed Structure (CCP)
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