What is the coordination number of sodium in sodium oxide (`Na_2O`)?

Options

A. 6
B. 4
C. 8
D. 2

Answer

To determine the coordination number of sodium in sodium oxide (Na₂O), we can follow these steps:

### Step 1: Understand the Structure of Sodium Oxide
Sodium oxide (Na₂O) consists of sodium ions (Na⁺) and oxide ions (O²⁻). In this compound, the oxide ion acts as the anion, while sodium ions are the cations.

### Step 2: Identify the Lattice Structure
Sodium oxide adopts an anti-fluoride structure. In this structure, the oxide ions form a face-centered cubic (FCC) lattice.

### Step 3: Determine the Position of Sodium Ions
In the anti-fluoride structure, the sodium ions occupy the tetrahedral voids within the FCC lattice formed by the oxide ions.

### Step 4: Calculate the Coordination Number
The coordination number refers to the number of nearest neighbors surrounding a central atom or ion. In this case, each sodium ion (Na⁺) is surrounded by four oxide ions (O²⁻) in the tetrahedral arrangement. Therefore, the coordination number of sodium in sodium oxide is 4.

### Final Answer
The coordination number of sodium in sodium oxide (Na₂O) is 4.

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