The atomic radii of first group elements are given below:
`{:("Group - 1 element Atomic Radii (pm) "),(" Na 186"),(" K 231"),(" Rb 244"),(" Cs 282"):}`
State the reason behind the observed trend in the above elements.

Explanation

To explain the observed trend in the atomic radii of the first group elements (alkali metals) as we move down the group, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Elements and Their Atomic Radii**:
- Sodium (Na): 186 pm
- Potassium (K): 231 pm
- Rubidium (Rb): 244 pm
...