Which is the non-lanthanide element ?

Options

A. La
B. Lu
C. Pr
D. Pm

Explanation

To determine which element is a non-lanthanide element, we need to first understand what lanthanides are and identify the elements in that series.

### Step-by-Step Solution:

1. **Definition of Lanthanides**:
- Lanthanides are a series of 15 elements from atomic number 57 (Lanthanum) to 71 (Lutetium). These elements are characterized by the filling of the 4f subshell.

2. **Identify the Elements**:
- The lanthanide series includes the following elements:
- Lanthanum (La, 57)
- Cerium (Ce, 58)
- Praseodymium (Pr, 59)
- Neodymium (Nd, 60)
- Promethium (Pm, 61)
- Samarium (Sm, 62)
- Europium (Eu, 63)
- Gadolinium (Gd, 64)
- Terbium (Tb, 65)
- Dysprosium (Dy, 66)
- Holmium (Ho, 67)
- Erbium (Er, 68)
- Thulium (Tm, 69)
- Ytterbium (Yb, 70)
- Lutetium (Lu, 71)

3. **Identify Non-Lanthanide Elements**:
- Any element that does not fall within the atomic numbers 57 to 71 is considered a non-lanthanide element.
- For example, elements like Scandium (Sc, 21), Titanium (Ti, 22), and Hafnium (Hf, 72) are not part of the lanthanide series.

4. **Conclusion**:
- Based on the information provided, the non-lanthanide element among the options is **Hafnium (Hf)**, which has the atomic number 72 and is part of the d-block elements, not the f-block (lanthanides).

### Answer:
The non-lanthanide element is **Hafnium (Hf)**.