The one of the rarest element of group 18 is

Options

A. He
B. Ar
C. Ne
D. Xe

Answer

To determine the rarest element of Group 18 (the noble gases), we can follow these steps:

### Step-by-Step Solution:

1. **Identify Group 18 Elements**:
Group 18 of the periodic table consists of the noble gases, which include Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn).

2. **Understand Rarity**:
Rarity in this context refers to how commonly these gases are found in the Earth's atmosphere or in nature.

3. **Analyze Each Element**:
- **Helium (He)**: This is the second most abundant element in the universe, primarily found in natural gas deposits.
- **Neon (Ne)**: Neon is relatively rare but is used in neon signs and is found in trace amounts in the atmosphere.
- **Argon (Ar)**: Argon is the most abundant noble gas in the Earth's atmosphere, making up about 0.93% of the air.
- **Krypton (Kr)**: Krypton is rarer than argon and is found in trace amounts in the atmosphere.
- **Xenon (Xe)**: Xenon is also rare and found in very small quantities.
- **Radon (Rn)**: Radon is a radioactive noble gas that is rare and occurs naturally in the decay of uranium and thorium.

4. **Determine the Rarest Element**:
Among these elements, Radon (Rn) is considered one of the rarest due to its radioactive nature and limited occurrence in the environment. However, in terms of abundance in the atmosphere, Krypton and Xenon are rarer than Argon.

5. **Select the Correct Answer**:
Based on the options provided in the question (Helium, Argon, Neon, Xenon), the rarest noble gas in terms of atmospheric abundance is **Xenon**. However, if the question refers to the rarest in terms of natural occurrence, Radon would be the answer, but it is not listed among the options.

### Final Answer:
The one of the rarest elements of Group 18 is **Xenon**.