Three elements 'X', 'Y' and 'Z' have atomic numbers 7, 8 and 9 respectively.
Arrange these elements in the decreasing order of their atomic radii.

Explanation

To solve the problem of arranging the elements 'X', 'Y', and 'Z' with atomic numbers 7, 8, and 9 in decreasing order of their atomic radii, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Elements**:
- The atomic number 7 corresponds to Nitrogen (N).
- The atomic number 8 corresponds to Oxygen (O).
- The atomic number 9 corresponds to Fluorine (F).
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