Which of the two cations `Mg^(2+)` and `Al^(3+)` is smaller?

Explanation

To determine which of the two cations, \( Mg^{2+} \) or \( Al^{3+} \), is smaller, we can follow these steps:

### Step 1: Identify the number of protons and electrons in each cation.
- **For \( Mg^{2+} \)**:
- Atomic number of Magnesium (Mg) = 12
- Number of protons = 12
- Number of electrons after losing 2 electrons = 12 - 2 = 10

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