Boron forms only `"………….."` compounds while aluminium forms both `"………….."` and `"………….."`compounds.

Answer

To answer the question, we need to analyze the properties of boron and aluminum in terms of the types of compounds they form.

### Step-by-Step Solution:

1. **Understanding Boron**:
- Boron is classified as a metalloid. Metalloids typically have properties that are intermediate between metals and non-metals.
- Due to its small size and high electronegativity, boron tends to form covalent bonds rather than ionic bonds.

2. **Compounds Formed by Boron**:
- Since boron is a metalloid and forms covalent bonds, we conclude that boron forms only **covalent compounds**.

3. **Understanding Aluminum**:
- Aluminum, on the other hand, is classified as a metal. Metals generally have a tendency to lose electrons and form positive ions.
- Aluminum can form both covalent and ionic bonds due to its metallic character and its ability to form ions.

4. **Compounds Formed by Aluminum**:
- Therefore, aluminum can form **covalent compounds** (like AlCl3) and **ionic compounds** (like Al2O3).

5. **Filling in the Blanks**:
- Based on the analysis, we can fill in the blanks:
- Boron forms only **covalent** compounds.
- Aluminum forms both **covalent** and **ionic** compounds.

### Final Answer:
Boron forms only **covalent** compounds while aluminum forms both **covalent** and **ionic** compounds.