Write two reasons behind the anomalous behaviour of first element of each group.

Explanation

To address the question regarding the anomalous behavior of the first element of each group in the s-block elements, we can outline two primary reasons:

### Step-by-Step Solution:

1. **Small Atomic Size**:
- The first element of each group (like Li, Be, Na, etc.) has a smaller atomic size compared to the other elements in the same group. This smaller size leads to a higher charge density and affects the physical and chemical properties of these elements, making them behave differently from their heavier counterparts.

2. **High Effective Nuclear Charge**:
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