From the given list, how many pairs of elements form ionic bonds when they react?
Bromine, Carbon, Iron, Sodium, Sulphur

Explanation

To determine how many pairs of elements from the given list form ionic bonds when they react, we need to analyze the nature of each element and their possible combinations.

### Step-by-Step Solution:

1. **Identify the Nature of Each Element:**
- **Bromine (Br)**: Non-metal
- **Carbon (C)**: Non-metal
- **Iron (Fe)**: Metal
- **Sodium (Na)**: Metal
- **Sulphur (S)**: Non-metal

2. **Determine Possible Ionic Bonding Pairs:**
Ionic bonds typically form between metals and non-metals due to the transfer of electrons from the metal to the non-metal.

3. **Evaluate Each Pair:**
- **Bromine (Br) and Sodium (Na)**: Forms NaBr (ionic bond).
- **Bromine (Br) and Iron (Fe)**: Can form FeBr3 (ionic bond).
- **Bromine (Br) and Sulphur (S)**: Does not typically form an ionic bond (both are non-metals).
- **Bromine (Br) and Carbon (C)**: Does not typically form an ionic bond (both are non-metals).
- **Iron (Fe) and Sulphur (S)**: Forms FeS (ionic bond).
- **Iron (Fe) and Carbon (C)**: Typically forms covalent bonds (not ionic).
- **Sodium (Na) and Sulphur (S)**: Can form Na2S (ionic bond).
- **Sodium (Na) and Carbon (C)**: Typically forms covalent bonds (not ionic).

4. **Count the Valid Ionic Bonding Pairs:**
- Valid pairs that form ionic bonds:
- Na and Br
- Fe and Br
- Fe and S
- Na and S

Thus, we have a total of **4 pairs** that can form ionic bonds.

### Final Answer:
**4 pairs of elements form ionic bonds.**

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