To determine the correct order of radii for the given elements and ions, we need to analyze each option based on the principles of atomic and ionic radii.
### Step-by-Step Solution:
1. **Option 1: Sodium (Na), Magnesium (Mg), Aluminum (Al)**
- These elements are in the same period (Period 3).
- As we move from left to right across a period, the effective nuclear charge (Z_eff) increases because the number of protons increases while the shielding effect remains relatively constant.
- This increase in Z_eff pulls the electrons closer to the nucleus, resulting in a decrease in atomic radius.
- Therefore, the order of radii is:
\[ \text{Na} > \text{Mg} > \text{Al} \]
- **Conclusion for Option 1:** Correct order is Na > Mg > Al.
2. **Option 2: Na⁺, Mg²⁺, Al³⁺**
- These ions are isoelectronic, meaning they have the same number of electrons (10 electrons).
- However, they have different nuclear charges: Na⁺ has 11 protons, Mg²⁺ has 12 protons, and Al³⁺ has 13 protons.
- As the positive charge increases, the ionic radius decreases due to the increased attraction between the nucleus and the electrons.
- Therefore, the order of ionic radii is:
\[ \text{Na}^+ > \text{Mg}^{2+} > \text{Al}^{3+} \]
- **Conclusion for Option 2:** Correct order is Na⁺ > Mg²⁺ > Al³⁺.
3. **Option 3: I⁻, I, I⁺**
- Here, we have anions and cations of iodine.
- The ionic radius of an anion (I⁻) is larger than that of a neutral atom (I), which in turn is larger than that of a cation (I⁺).
- Therefore, the order of radii is:
\[ \text{I}^- > \text{I} > \text{I}^+ \]
- **Conclusion for Option 3:** Correct order is I⁻ > I > I⁺.
4. **Option 4: Nitrogen (N), Helium (He), Neon (Ne)**
- Helium and Neon are noble gases, and their radii are measured as Van der Waals radii.
- As we move down a group, the atomic radius increases due to the addition of electron shells.
- Thus, the order of radii is:
\[ \text{He} < \text{N} < \text{Ne} \]
- **Conclusion for Option 4:** Correct order is He < N < Ne.
### Final Summary of Correct Orders:
- **Option 1:** Na > Mg > Al
- **Option 2:** Na⁺ > Mg²⁺ > Al³⁺
- **Option 3:** I⁻ > I > I⁺
- **Option 4:** He < N < Ne
