The most abundant inert gas is___________.

Explanation

**Step-by-Step Solution:**

1. **Identify the Inert Gases**: The inert gases, also known as noble gases, include Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn).

2. **Understand Their Occurrence in the Atmosphere**: Most of these gases are found in the Earth's atmosphere, except for Radon, which is a radioactive element and not present in significant amounts.

3. **Check the Abundance of Each Inert Gas**:
- Helium (He): approximately 0.00053%
- Neon (Ne): approximately 0.0018%
- Argon (Ar): approximately 0.95%
- Krypton (Kr): approximately 0.0001%
- Xenon (Xe): approximately 0.00087%
- Radon (Rn): not present in the atmosphere

4. **Determine the Most Abundant Inert Gas**: From the abundance percentages, Argon (Ar) has the highest percentage at approximately 0.95%.

5. **Conclusion**: Therefore, the most abundant inert gas in the atmosphere is Argon.

**Final Answer**: The most abundant inert gas is **Argon**.

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