Select from each group the species which has the smallest radius stating appropriate reason
`K^(+), Sr^(2+), Ar`

Explanation

To determine which species has the smallest radius among \( K^+, Sr^{2+}, \) and \( Ar \), we can follow these steps:

### Step 1: Understand the nature of the species
We have two cations (\( K^+ \) and \( Sr^{2+} \)) and one neutral atom (\( Ar \)). Cations are positively charged ions formed when an atom loses electrons, while a neutral atom has an equal number of protons and electrons.

**Hint:** Remember that cations are generally smaller than their parent atoms due to the loss of electrons and the resulting increase in effective nuclear charge.

### Step 2: Compare the ionic sizes
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