All the lanthanoids in actioniods belong to group …….. Of the periodic table.

Explanation

To determine the group of the periodic table to which all the lanthanoids and actinoids belong, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Periodic Table Structure**:
The periodic table is organized into groups (columns) and periods (rows). There are 18 groups in the modern periodic table.

2. **Identify Lanthanoids and Actinoids**:
- Lanthanoids are the series of elements from atomic number 57 (Lanthanum) to 71 (Lutetium).
- Actinoids are the series of elements from atomic number 89 (Actinium) to 103 (Lawrencium).

3. **Locate Their Position in the Periodic Table**:
- Both lanthanoids and actinoids are typically placed in the f-block of the periodic table.
- They are often shown separately at the bottom of the periodic table.

4. **Determine Their Group**:
- Lanthanum (La) is in Group 3, and it is the first element of the lanthanoid series.
- Actinium (Ac) is also in Group 3, and it is the first element of the actinoid series.
- Therefore, both lanthanoids and actinoids belong to Group 3 of the periodic table.

5. **Conclusion**:
All the lanthanoids and actinoids belong to Group 3 of the periodic table.

### Final Answer:
All the lanthanoids and actinoids belong to Group 3 of the periodic table.

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