Which of the following is not a noble gas?
A) oganesson
B) Argon
C) Xenon
D) Chlorine

Options

A. oganesson
B. Argon
C. Xenon
D. Chlorine

Answer

To determine which of the following options is not a noble gas, we need to understand what noble gases are and identify each option provided.

### Step-by-Step Solution:

1. **Understand Noble Gases**: Noble gases are a group of chemical elements that are characterized by their lack of reactivity due to having a full outer shell of electrons. This group includes Helium, Neon, Argon, Krypton, Xenon, and Radon.

2. **Analyze Each Option**:
- **Option A: Oganesson (Og)** - This is a noble gas with the atomic number 118. It is considered a noble gas despite being a synthetic element.
- **Option B: Argon (Ar)** - This is a well-known noble gas with the atomic number 18. It has a full outer electron shell.
- **Option C: Xenon (Xe)** - This is also a noble gas with the atomic number 54, and it has a complete outer shell.
- **Option D: Chlorine (Cl)** - Chlorine has the atomic number 17 and is classified as a halogen. Its outer shell is not full, which makes it reactive.

3. **Identify the Non-Noble Gas**: From the analysis, we see that Chlorine (Option D) is not a noble gas because it does not have a full outer electron shell and is reactive.

4. **Conclusion**: Therefore, the answer to the question "Which of the following is not a noble gas?" is **Option D: Chlorine**.