Which of the following is not representative element?

Options

A. Tellurium
B. Tantalum
C. Thallium
D. Astatine

Explanation

To determine which of the given elements is not a representative element, we need to identify the block to which each element belongs. Representative elements are those found in the S and P blocks of the periodic table.

### Step-by-Step Solution:

1. **Identify the Elements and Their Blocks**:
- **Tellurium (Te)**:
- Atomic Number: 52
- Block: P block (it belongs to the oxygen family).

- **Tantalum (Ta)**:
- Atomic Number: 73
- Block: D block (it is a transition metal).

- **Helium (He)**:
- Atomic Number: 2
- Block: S block (it is a noble gas).

- **Ethylene**:
- Note: Ethylene is not an element but a compound (C2H4). However, if we consider the individual elements in ethylene, we have Carbon (C) and Hydrogen (H).
- Carbon (C): Atomic Number: 6, Block: P block.
- Hydrogen (H): Atomic Number: 1, Block: S block.

2. **Determine Which Element is Not a Representative Element**:
- From the analysis:
- Tellurium (Te) is in the P block.
- Tantalum (Ta) is in the D block (not a representative element).
- Helium (He) is in the S block.
- The elements in ethylene (C and H) are in the S and P blocks.

3. **Conclusion**:
- The element that is not a representative element is **Tantalum (Ta)**, as it belongs to the D block (transition metals).

### Final Answer:
**Tantalum (Ta)** is not a representative element.