Which element in each of the following pairs of elements would you expect to have lower first ionisation energy? Explain.
K, Ar

Explanation

To determine which element has a lower first ionization energy between potassium (K) and argon (Ar), we can follow these steps:

### Step 1: Identify the Atomic Numbers
- Potassium (K) has an atomic number of 19.
- Argon (Ar) has an atomic number of 18.

### Step 2: Write the Electronic Configurations
- The electronic configuration of potassium (K) is:
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