What do you understand by Representative elements ? Name the groups whose elements are called representative elements.

Explanation

### Step-by-Step Text Solution:

1. **Definition of Representative Elements**:
Representative elements are those elements that belong to specific groups in the periodic table and exhibit a wide range of physical and chemical properties. They are considered "representative" because they showcase the characteristics of their respective groups.

2. **Identification of Groups**:
The representative elements include:
- **Group 1**: Alkali metals
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