Which of the following orders of atomic radii is correctly represented?

Options

A. `B lt Al lt Ga`
B. `B lt Ga lt Al`
C. `Al lt B lt Ga`
D. `B gt Ga gt Al`

Explanation

To determine the correct order of atomic radii for Boron (B), Aluminum (Al), and Gallium (Ga), we need to analyze the trends in atomic size within the periodic table, particularly focusing on group 13 elements.

### Step-by-Step Solution:

1. **Identify the Elements and Their Periods**:
- Boron (B) is in the 2nd period.
- Aluminum (Al) is in the 3rd period.
- Gallium (Ga) is in the 4th period.

2. **Understand the Trend in Atomic Radii**:
- As we move down a group in the periodic table, the atomic radius generally increases. This is because each successive element has an additional electron shell, which increases the distance between the nucleus and the outermost electrons.

3. **Analyze the Atomic Radii of the Elements**:
- For Boron (2 shells), Aluminum (3 shells), and Gallium (4 shells), we can expect that:
- Boron will have the smallest atomic radius.
- Aluminum will have a larger atomic radius than Boron.
- Gallium will have a larger atomic radius than Aluminum, but we need to consider the effects of d-block elements.

4. **Consider the Screening Effect**:
- Gallium is affected by the presence of d-block elements (transition metals) in the 4th period. The d-electrons provide a poor screening effect, which means that the effective nuclear charge felt by the valence electrons of Gallium is higher than that of Aluminum.
- This results in Gallium having a smaller atomic radius compared to what we would expect if we only considered the addition of electron shells.

5. **Determine the Correct Order**:
- Based on the above analysis, the correct order of atomic radii is:
- Boron (B) > Aluminum (Al) > Gallium (Ga)
- Thus, the correct representation of the order of atomic radii is:
- B < Al < Ga

### Final Answer:
The correct order of atomic radii is: **Boron < Aluminum < Gallium**.