All the lanthanoids and actinoids belong to period of

Options

A. 5th and 6th respectively
B. 6th and 7th respectively
C. 5th and 7th respectively
D. either (1)(2)

Answer

To determine the periods to which all the lanthanoids and actinoids belong, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Periodic Table Structure**:
- The modern periodic table is organized into periods (horizontal rows) and groups (vertical columns). There are 7 periods in total in the modern periodic table.

2. **Identifying Lanthanoids and Actinoids**:
- Lanthanoids are a series of 15 elements from Lanthanum (La, atomic number 57) to Lutetium (Lu, atomic number 71).
- Actinoids are a series of 15 elements from Actinium (Ac, atomic number 89) to Lawrencium (Lr, atomic number 103).

3. **Locating Lanthanoids in the Periodic Table**:
- Lanthanoids are found in the sixth period of the periodic table. They are placed in the f-block, which is located below the main body of the periodic table.

4. **Locating Actinoids in the Periodic Table**:
- Actinoids are found in the seventh period of the periodic table. Similar to lanthanoids, they are also placed in the f-block.

5. **Conclusion**:
- Therefore, all lanthanoids belong to the sixth period, and all actinoids belong to the seventh period of the periodic table.

### Final Answer:
All the lanthanoids belong to the **6th period**, and all the actinoids belong to the **7th period** of the periodic table.

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