Write the formulae of sodium sulphide

Explanation

To write the formula of sodium sulfide, follow these steps:

### Step 1: Identify the elements involved
- Sodium (Na) and Sulfur (S) are the two elements that make up sodium sulfide.

### Step 2: Determine the valency of each element
- Sodium (Na) has a valency of +1. This means it tends to lose one electron and form a Na⁺ ion.
- Sulfur (S) in the form of sulfide (S²⁻) has a valency of -2. This means it gains two electrons to form a S²⁻ ion.
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