Which of the following has the maximum atomic radius?

Options

A. Al
B. Si
C. P
D. Mg

Explanation

To determine which of the given elements has the maximum atomic radius, we need to analyze the elements based on their position in the periodic table. The elements provided are Aluminum (Al), Silicon (Si), Phosphorus (P), and Magnesium (Mg).

### Step-by-Step Solution:

1. **Identify the Elements and Their Groups/Periods**:
- Magnesium (Mg) - Group 2, Period 3
- Aluminum (Al) - Group 13, Period 3
- Silicon (Si) - Group 14, Period 3
- Phosphorus (P) - Group 15, Period 3

2. **Understand Atomic Radius Trends**:
- Atomic radius generally decreases across a period from left to right. This is because as you move across a period, the number of protons in the nucleus increases, which increases the positive charge (Z-effective). This increased positive charge pulls the electrons closer to the nucleus, resulting in a smaller atomic radius.
- Atomic radius generally increases down a group. This is due to the addition of electron shells, which outweighs the increase in nuclear charge.

3. **Compare the Elements**:
- All four elements (Mg, Al, Si, P) are in the same period (Period 3). Therefore, we will compare their atomic radius based on their group numbers.
- As per the trend, Magnesium (Group 2) will have a larger atomic radius than Aluminum (Group 13), Silicon (Group 14), and Phosphorus (Group 15) because it is further to the left in the periodic table.

4. **Conclusion**:
- Among the given elements, Magnesium (Mg) has the maximum atomic radius because it is in Group 2, which is to the left of the other elements in the same period.

### Final Answer:
**Magnesium (Mg) has the maximum atomic radius among the given elements.**