How do atomic radii vary in a period and in a group ? How do you explain the variation ?

Explanation

### Step-by-Step Solution:

1. **Understanding Atomic Radii**:
- Atomic radius is the distance from the nucleus of an atom to the outermost shell of electrons.
- It is an important property that helps in understanding the size of atoms.

2. **Variation in a Period**:
- As you move from left to right across a period in the periodic table, the atomic radius **decreases**.
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