Write down the electronic configuration of the following elements from the given atomic numbers. Answer the following question with explanation.
`._(19)K, ._(3)Li, ._(11)Na, ._(4)Be`
Which of these atoms has the smallest atomic radius?

Explanation

To solve the question, we need to write the electronic configurations of the elements with the given atomic numbers and then determine which of these elements has the smallest atomic radius. Let's go through the steps one by one.

### Step 1: Write the electronic configuration for each element.

1. **Potassium (K, Atomic Number 19)**:
- The electronic configuration is filled in order of increasing energy levels:
- K: 2 electrons in the first shell, 8 in the second, 8 in the third, and 1 in the fourth shell.
- Therefore, the electronic configuration is: **1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹**.
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