The size of ionic species is correctly given in the order

Options

A. `Na^(+) gt Mg^(+2) gt CI^(+7) gt Sj^(4+)`
B. `Na^(+) gt Mg^(+2) gt Si^(4+) gt CI^(+7)`
C. `CI^(+7) gt Si^(+4) gt Mg^(+2) gt Na^(+)`
D. `CI^(+7) gt Na^(+) gt Mg^(+7) gt Si^(+4)`

Answer

To determine the correct order of ionic sizes for the given species (Na⁺, Mg²⁺, Cl⁻, and Si⁴⁺), we need to analyze their electronic configurations and the effect of charge on ionic size.

### Step-by-Step Solution:

1. **Identify the Ions and Their Charges**:
- Sodium ion (Na⁺) has a +1 charge.
- Magnesium ion (Mg²⁺) has a +2 charge.
- Chloride ion (Cl⁻) has a -1 charge.
- Silicon ion (Si⁴⁺) has a +4 charge.

2. **Determine the Number of Electrons**:
- All these ions are isoelectronic, meaning they have the same number of electrons. In this case, they all have 10 electrons, which is the same as the electron configuration of Neon (Ne).

3. **Understand the Effect of Charge on Ionic Size**:
- The size of an ion is influenced by its charge. As the positive charge on an ion increases, the size of the ion decreases due to the increased attraction between the nucleus and the electrons.
- Conversely, a negative charge leads to an increase in size due to the repulsion between the electrons.

4. **Rank the Ions Based on Charge**:
- Na⁺ (1+ charge) will be larger than Mg²⁺ (2+ charge) because Na⁺ has less positive charge pulling on the same number of electrons.
- Mg²⁺ will be larger than Si⁴⁺ (4+ charge) for the same reason.
- Cl⁻ (1- charge) will be larger than all the positively charged ions because it has an extra electron, leading to increased electron-electron repulsion.

5. **Final Order of Ionic Sizes**:
- Based on the above reasoning, the correct order of ionic sizes from largest to smallest is:
- Na⁺ > Cl⁻ > Mg²⁺ > Si⁴⁺

### Conclusion:
The size of ionic species is correctly given in the order: **Na⁺ > Cl⁻ > Mg²⁺ > Si⁴⁺**.