Why sodium chloride on heating with sodium vapours acquires yellow colour?

Explanation

To understand why sodium chloride (NaCl) acquires a yellow color when heated with sodium vapors, we can break down the explanation into several steps:

### Step-by-Step Solution

1. **Heating Sodium Chloride with Sodium Vapors**:
- When sodium chloride is heated in the presence of sodium vapors, sodium atoms are deposited onto the sodium chloride crystals. This process leads to an excess of sodium in the system.

2. **Departure of Chlorine**:
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