The elements in which 4f orbitals are progressively field up are called as

Options

A. actinoids
B. transition elements
C. lanthanoids
D. halogens

Explanation

To answer the question "The elements in which 4f orbitals are progressively filled up are called as," we will analyze the options provided and identify the correct answer step by step.

### Step-by-Step Solution:

1. **Understanding the 4f Orbitals**:
The 4f orbitals are part of the f-block in the periodic table. The filling of these orbitals occurs as we move through the lanthanide series.

2. **Identifying the Elements**:
- The lanthanides are the elements that have their 4f orbitals progressively filled. These elements range from atomic number 57 (Lanthanum) to atomic number 71 (Lutetium).

3. **Analyzing the Options**:
- **Option A: Actinoids**: These elements fill the 5f orbitals (not 4f), ranging from atomic number 89 to 103. Therefore, this option is incorrect.
- **Option B: Transition Elements**: These are d-block elements and do not fill the 4f orbitals. Hence, this option is also incorrect.
- **Option C: Lanthanoids**: These elements fill the 4f orbitals progressively from atomic number 57 to 71. This is the correct option.
- **Option D: Halogens**: These are p-block elements and do not involve the filling of 4f orbitals. Thus, this option is incorrect.

4. **Conclusion**:
The elements in which the 4f orbitals are progressively filled up are called **lanthanoids**.

### Final Answer:
The elements in which 4f orbitals are progressively filled up are called **lanthanoids**.