Which of the following pair of elements have same atomic radius

Options

A. B, AI
B. Al, Ga
C. Ga, In
D. B,TI

Answer

To determine which pair of elements has the same atomic radius, we can follow these steps:

### Step 1: Understand Atomic Radius
The atomic radius is the distance from the nucleus of an atom to the outermost shell of electrons. It generally increases down a group in the periodic table due to the addition of electron shells.

### Step 2: Identify the Elements in the Question
The pairs of elements given in the question are:
1. Boron (B) and Aluminium (Al)
2. Aluminium (Al) and Gallium (Ga)
3. Gallium (Ga) and Indium (In)
4. Boron (B) and Thallium (Tl)

### Step 3: Analyze Each Pair
- **Boron (B) and Aluminium (Al)**: Boron is in period 2, and Aluminium is in period 3. Typically, the atomic radius of Aluminium is larger than that of Boron.

- **Aluminium (Al) and Gallium (Ga)**: Both elements are in the same group (Group 13). However, Gallium has a d-orbital that leads to poor shielding effect. This results in a similar effective nuclear charge experienced by the outermost electrons in both elements, causing them to have similar atomic radii.

- **Gallium (Ga) and Indium (In)**: Indium is in period 5, and it is expected to have a larger atomic radius than Gallium due to the additional electron shell.

- **Boron (B) and Thallium (Tl)**: Thallium is in period 6, and it would have a larger atomic radius than Boron.

### Step 4: Conclusion
From the analysis, the pair that has the same atomic radius is **Aluminium (Al) and Gallium (Ga)** due to the poor shielding effect of the d-orbitals in Gallium.

### Final Answer
**The pair of elements that have the same atomic radius is Aluminium (Al) and Gallium (Ga).**

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