Which of the following has the smallest size

Options

A. `Na^(+)`
B. `Mg^(+2)`
C. `Cl^(-)`
D. `F^(-)`

Explanation

To determine which of the given options has the smallest size, we need to analyze the sizes of different ions and neutral atoms based on their charge and electron configuration. Here’s a step-by-step solution:

### Step 1: Understand Ion Sizes
- The size of an atom or ion is influenced by its charge. Generally, cations (positively charged ions) are smaller than their neutral atoms because they lose electrons, which reduces electron-electron repulsion and allows the nucleus to pull the remaining electrons closer.
- Conversely, anions (negatively charged ions) are larger than their neutral atoms because they gain electrons, increasing electron-electron repulsion.

### Step 2: Compare the Sizes of Different Species
- Let's consider the following species: N (neutral nitrogen), N³⁻ (nitride ion), Na⁺ (sodium ion), Mg²⁺ (magnesium ion), Cl⁻ (chloride ion), and F⁻ (fluoride ion).
- The order of size based on charge is as follows:
- Anions (larger): Cl⁻ > F⁻ > N³⁻
- Neutral: N
- Cations (smaller): Na⁺ > Mg²⁺

### Step 3: Identify the Smallest Ion
- From the comparison:
- Cl⁻ and F⁻ are larger than their neutral counterparts.
- N³⁻ is larger than N.
- Among the cations, Na⁺ is larger than Mg²⁺.
- Therefore, Mg²⁺ is the smallest ion among the given options.

### Conclusion
- The species with the smallest size is **Mg²⁺**.