Which of the following is the wrong statement?

Options

A. All the actinoid elements are radioactive
B. Alkali and alkaline earth metals are s - block elements
C. Chalcogens and halogens are p - block elements
D. The first member of the lanthanoid series is lanthanum

Answer

To identify the wrong statement among the given options, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: All actinoids are radioactive.**
- The actinoids are elements in the 5f series, which includes elements from actinium (Ac) to lawrencium (Lr). It is well-known that all actinoids are indeed radioactive.
- **Conclusion:** This statement is **true**.

2. **Statement 2: Alkali and Alkaline Earth metals are associated.**
- Alkali metals (Group 1) have the general electronic configuration of ns¹, while alkaline earth metals (Group 2) have ns². Both groups are located in the s-block of the periodic table.
- **Conclusion:** This statement is **true**.

3. **Statement 3: Chalcogens and Halogens are p-block elements.**
- Chalcogens (Group 16) have the electronic configuration ns²p⁴, and halogens (Group 17) have ns²p⁵. Both groups are indeed classified as p-block elements in the periodic table.
- **Conclusion:** This statement is **true**.

4. **Statement 4: The first member of the lanthanide series is lanthanum.**
- The lanthanide series consists of elements from lanthanum (La) to lutetium (Lu). The first member of the lanthanide series is indeed lanthanum, not cerium.
- **Conclusion:** This statement is **false**.

### Final Answer:
The wrong statement is: **The first member of the lanthanide series is lanthanum.**