General science (chemistry): Identify the most abundant noble (rare) gas present in Earth’s atmosphere. Among the noble gases (He, Ne, Ar, Kr, Xe), which gas occurs in the highest proportion in dry air at sea level? Choose the correct option.

Given / Recall

• Noble (rare) gases in air include He, Ne, Ar, Kr, Xe.
• Dry air composition by volume: N₂ ~78%, O₂ ~21%, Ar ~0.93%, CO₂ ~0.04%.

Concept
Among noble gases, the gas with the greatest atmospheric fraction is considered the most abundant.

Reasoning
Argon is ~0.93% of dry air, far exceeding neon (~18 ppm), helium (~5 ppm), krypton (~1 ppm), xenon (~0.09 ppm).

Common pitfalls
Confusing overall abundance in the universe (He) with abundance in Earth’s atmosphere (Ar).

Final Answer
Argon (Ar).