The increasing order of atomic radii of the following group 13 elements is

Options

A. `B lt Ga lt Al lt Tl lt "In"`
B. `B lt Al lt Ga lt "In" lt TI`
C. `B lt Al lt "In" lt Ga lt TI`
D. `B lt Ga lt Al lt "In" lt TI`

Explanation

To determine the increasing order of atomic radii of the group 13 elements (Boron, Aluminum, Gallium, Indium, and Thallium), we need to analyze the trends in atomic size within this group.

### Step-by-Step Solution:

1. **Understanding Atomic Radii Trends**:
- Generally, atomic radii increase down a group in the periodic table due to the addition of electron shells. However, there are exceptions due to the effects of electron shielding and effective nuclear charge.

2. **Identify the Elements**:
- The group 13 elements we are considering are:
- Boron (B)
- Aluminum (Al)
- Gallium (Ga)
- Indium (In)
- Thallium (Tl)

3. **General Trend in Group 13**:
- As we move down the group, we expect the atomic radius to increase. However, we need to pay attention to the specific case of Gallium.

4. **Gallium's Anomaly**:
- Gallium's atomic radius is smaller than that of Aluminum. This is due to the presence of d-electrons in Gallium, which do not shield the nucleus effectively. The effective nuclear charge felt by the outermost electrons in Gallium is higher than that in Aluminum, leading to a smaller atomic radius for Gallium.

5. **Comparing Atomic Radii**:
- Based on the above analysis, we can summarize the atomic radii from smallest to largest:
- Boron (smallest)
- Gallium (smaller than Aluminum)
- Aluminum
- Indium
- Thallium (largest)

6. **Final Order**:
- Therefore, the increasing order of atomic radii for the group 13 elements is:
- Boron < Gallium < Aluminum < Indium < Thallium

### Conclusion:
The correct answer is Option D: Boron < Gallium < Aluminum < Indium < Thallium.