Which of the following elements is not an f-block element?

Options

A. No
B. Nd
C. Nb
D. Np

Answer

To determine which of the given elements is not an f-block element, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understand f-block Elements**:
- The f-block elements consist of the lanthanides and actinides. Lanthanides include elements with atomic numbers 57 to 71 (from lanthanum to lutetium), and actinides include elements with atomic numbers 89 to 103 (from actinium to lawrencium).

2. **Identify the Elements**:
- Let's identify the elements mentioned in the question:
- Nobellium (No) - Atomic number 102, which is an actinide and hence an f-block element.
- Neodymium (Nd) - Atomic number 60, which is a lanthanide and hence an f-block element.
- Neptunium (Np) - Atomic number 93, which is an actinide and hence an f-block element.
- The element represented by "N" is not specified, but if we assume it refers to Nitrogen (N), it has an atomic number of 7 and is not an f-block element.

3. **Conclusion**:
- Among the elements listed, Nitrogen (N) is not an f-block element, while Nobellium, Neodymium, and Neptunium are all f-block elements.

4. **Final Answer**:
- The element that is not an f-block element is **Nitrogen (N)**.