Which of the following is the wrong statements?

Options

A. All the actinide elements are radioactive.
B. Alkali and alkaline earth metals are `s`-block elements.
C. Pnicogens and halogens are `p`-block elements.
D. The first member of the lanthanide series is lanthanum.

Explanation

To determine which of the following statements is incorrect, we will analyze each statement one by one.

1. **Statement 1**: "All actinide elements are radioactive."
- **Analysis**: Actinides are the series of elements from actinium (Ac, atomic number 89) to lawrencium (Lr, atomic number 103). All actinides are indeed radioactive. Therefore, this statement is **true**.

2. **Statement 2**: "Alkali and alkaline earth metals are s-block elements."
- **Analysis**: Alkali metals (Group 1) and alkaline earth metals (Group 2) are both located in the s-block of the periodic table. Hence, this statement is also **true**.

3. **Statement 3**: "Nitrogens and halogens are p-block elements."
- **Analysis**: Nitrogens (Group 15) and halogens (Group 17) are indeed classified as p-block elements in the periodic table. Thus, this statement is **true**.

4. **Statement 4**: "The first member of the lanthanide series is lanthanum."
- **Analysis**: The lanthanide series starts with lanthanum (La, atomic number 57), but the first f-block element, which is often referred to in the context of the lanthanide series, is cerium (Ce, atomic number 58). Therefore, this statement is **false**.

Based on the analysis, the incorrect statement is:

**Answer**: The first member of the lanthanide series is lanthanum (Statement 4 is incorrect).

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