The radius of which is closest to that of the `Li^(+)` ions?

Options

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

Explanation

To determine which element's radius is closest to that of the `Li^(+)` ion, we can follow these steps:

### Step 1: Understand the Concept of Ionic Radius
The ionic radius of an ion is the measure of an ion's size. For cations (positively charged ions), the ionic radius is generally smaller than the atomic radius due to the loss of electrons, which results in a stronger effective nuclear charge on the remaining electrons.

### Step 2: Identify the Ionic Radius of `Li^(+)`
The ionic radius of `Li^(+)` (Lithium ion) is approximately 0.76 Å (angstroms). This is important as we will compare other ions' radii to this value.

### Step 3: Consider the Diagonal Relationship
In the periodic table, elements that are diagonally related often exhibit similar properties, including ionic radii. Lithium (Li) is in Group 1 (alkali metals), while Magnesium (Mg) is in Group 2 (alkaline earth metals). According to the diagonal relationship, the ionic radius of `Li^(+)` is expected to be similar to that of `Mg^(2+)`.

### Step 4: Compare with Other Ions
To find an ion with a radius close to `Li^(+)`, we can look at the ionic radii of common ions:
- `Na^(+)` (Sodium ion): ~1.02 Å
- `K^(+)` (Potassium ion): ~1.38 Å
- `Mg^(2+)` (Magnesium ion): ~0.72 Å
- `Ca^(2+)` (Calcium ion): ~1.00 Å

### Step 5: Identify the Closest Radius
From the comparison:
- The radius of `Mg^(2+)` (0.72 Å) is closest to the radius of `Li^(+)` (0.76 Å).

### Conclusion
Thus, the radius of `Mg^(2+)` is closest to that of `Li^(+)`.

### Final Answer
The radius closest to that of `Li^(+)` is that of `Mg^(2+)`.

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