Which of the following has largest size

Options

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

Explanation

To determine which of the given cations (Al⁺, Al²⁺, Al³⁺) has the largest size, we can follow these steps:

### Step 1: Understand the concept of cation size
Cations are positively charged ions formed when an atom loses one or more electrons. The loss of electrons results in a decrease in electron-electron repulsion and an increase in effective nuclear charge experienced by the remaining electrons.

**Hint:** Remember that cations are smaller than their parent atoms due to the loss of electrons.

### Step 2: Analyze the given cations
We have three cations to consider:
- Al⁺ (Aluminum with a +1 charge)
- Al²⁺ (Aluminum with a +2 charge)
- Al³⁺ (Aluminum with a +3 charge)

As the charge on the aluminum cation increases, the number of electrons decreases while the number of protons remains the same. This results in a stronger attraction between the nucleus and the remaining electrons.

**Hint:** More positive charge means a stronger pull on the remaining electrons.

### Step 3: Compare the effective nuclear charge
- For Al⁺: There are 13 protons and 12 electrons.
- For Al²⁺: There are 13 protons and 11 electrons.
- For Al³⁺: There are 13 protons and 10 electrons.

As we can see, as the cation charge increases from Al⁺ to Al³⁺, the effective nuclear charge increases because there are fewer electrons to shield the nucleus. This results in a stronger attraction of the nucleus to the remaining electrons, pulling them closer and reducing the size of the ion.

**Hint:** The more protons compared to electrons, the smaller the ion will be.

### Step 4: Determine the size trend
- Al⁺ has the largest size because it has the least effective nuclear charge acting on its electrons.
- Al²⁺ is smaller than Al⁺ but larger than Al³⁺.
- Al³⁺ has the smallest size due to the highest effective nuclear charge.

**Hint:** Remember that as the positive charge increases, the size of the cation decreases.

### Conclusion
Thus, the cation with the largest size among Al⁺, Al²⁺, and Al³⁺ is **Al⁺**.

**Final Answer:** Al⁺ has the largest size.