what is the corrdination number of
(i) Sodium in sodium oxide (` Na_(2)O)` ? (ii) oxide ion in sodim oxide `(Na_(2)O)` ?
(iii) Calcium in calcium fluoride ` (CaF_(2))` ? (iv) Zinc in zinc blende (ZnS) ?

Explanation

To determine the coordination numbers for the specified ions in the given compounds, we need to analyze the crystal structure of each compound. Here’s a step-by-step solution:

### Step 1: Coordination Number of Sodium in Sodium Oxide (Na₂O)
1. Sodium oxide consists of Na⁺ ions and O²⁻ ions.
2. In the crystal structure of Na₂O, the oxide ions (O²⁻) form a face-centered cubic (FCC) lattice.
3. Each O²⁻ ion is surrounded by 4 Na⁺ ions in a tetrahedral arrangement.
4. Therefore, the coordination number of sodium (Na⁺) in sodium oxide is **4**.

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