The set representing the correct order of ionic radius is : a)`Na^(+) gt Mg^(2+) gt Al^(3+) gt Be^(2+) gt Li^(+)` b)`Na^(+) gt Li^(+) gt Mg^(2+) gt Al^(3+) gt Be^(2+)` c)`Na^(+) gt Mg^(2+) gt Al^(3+) gt Li^(+) gt Be^(2+)` d)`Na^(+) gt Mg^(2+) gt Li^(+) gt Be^(2+) gt Al^(3+)`

Options

A. `Na^(+) gt Mg^(2+) gt Al^(3+) gt Li^(+) gt Be^(2+) `
B. `Na^(+) gt Li^(+) gt Mg^(2+) gt Al^(3+) gt Be^(2+) `
C. `Na^(+) gt Mg^(2+) gt Li^(+) gt Al^(3+) gt Be^(2+) `
D. `Na^(+) gt Mg^(2+) gt Li^(+) gt Be^(2+) `

Answer

To determine the correct order of ionic radius for the ions given in the question, we need to analyze the trends in ionic size based on their charge and position in the periodic table. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Understand Ionic Radius
The ionic radius is defined as the distance from the nucleus of an ion to the outermost electron shell. The size of ions can vary based on their charge and the number of electrons.

### Step 2: Analyze the Ions
We have the following ions to compare:
- Na⁺ (Sodium ion)
- Li⁺ (Lithium ion)
- Mg²⁺ (Magnesium ion)
- Al³⁺ (Aluminum ion)
- Be²⁺ (Beryllium ion)

### Step 3: Consider the Charge of the Ions
- Cations (positively charged ions) generally decrease in size as the charge increases because a higher positive charge pulls the remaining electrons closer to the nucleus.
- Therefore, for cations:
- Na⁺ > Li⁺ (Na⁺ has a larger radius than Li⁺)
- Mg²⁺ < Na⁺ (Mg²⁺ is smaller than Na⁺ due to a higher charge)
- Al³⁺ < Mg²⁺ (Al³⁺ is smaller than Mg²⁺ due to a higher charge)
- Be²⁺ < Al³⁺ (Be²⁺ is smaller than Al³⁺ due to a higher charge)

### Step 4: Compare the Sizes
From the analysis:
1. Na⁺ is the largest because it has the least positive charge.
2. Li⁺ is smaller than Na⁺.
3. Mg²⁺ is smaller than both Na⁺ and Li⁺.
4. Al³⁺ is smaller than Mg²⁺.
5. Be²⁺ is the smallest among these ions.

### Step 5: Order the Ions by Size
Based on the above comparisons, the order from largest to smallest ionic radius is:
- Na⁺ > Li⁺ > Mg²⁺ > Al³⁺ > Be²⁺

### Conclusion
The correct order of ionic radius is:
**Na⁺ > Li⁺ > Mg²⁺ > Al³⁺ > Be²⁺**

### Final Answer
The correct option is:
**b) Na⁺ > Li⁺ > Mg²⁺ > Al³⁺ > Be²⁺**