Name the element of group `13` which forms only covalent compounds.

Answer

To solve the question of which element in group 13 forms only covalent compounds, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Group 13 Elements**:
The elements in group 13 of the periodic table are boron (B), aluminium (Al), gallium (Ga), indium (In), and thallium (Tl).

2. **Understand the Nature of Compounds**:
Elements can form either covalent or ionic compounds. Covalent compounds are formed by the sharing of electrons, while ionic compounds are formed by the transfer of electrons.

3. **Analyze the Properties of Group 13 Elements**:
- **Boron**: It has a small atomic size and a high ionization enthalpy. This means it is difficult for boron to lose electrons and form positive ions.
- **Aluminium, Gallium, Indium, and Thallium**: As we move down the group, the atomic size increases, and the ionization enthalpy decreases, making it easier for these elements to lose electrons and form ionic compounds.

4. **Focus on Boron**:
Due to its small size and high ionization energy, boron does not readily lose electrons to form cations. Instead, it tends to share its electrons with other nonmetals, leading to the formation of covalent compounds.

5. **Conclusion**:
Therefore, the element of group 13 that forms only covalent compounds is **Boron (B)**.

### Final Answer:
Boron is the only element in group 13 that forms only covalent compounds.

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