Select the species which is best described
`CI,Ar,K` (has the smallest `IE`)

Explanation

To determine which species among Cl (Chlorine), Ar (Argon), and K (Potassium) has the smallest ionization energy (IE), we can follow these steps:

### Step 1: Understand Ionization Energy
Ionization energy is the energy required to remove an electron from a neutral atom in the gaseous state. The lower the ionization energy, the easier it is to remove an electron.

**Hint:** Remember that elements with fewer valence electrons tend to have lower ionization energies because they can achieve a stable electron configuration more easily by losing electrons.

### Step 2: Identify the Valence Electrons
...