Rare gases are a group of elements that are found in very small amounts in the atmosphere. ARGON, NEON, and XENON are all rare gases. ARGON is a colorless, odorless gas that is the most abundant of the rare gases, making up about 1% of the Earth's atmosphere. NEON is a colorless, odorless gas that is the second most abundant of the rare gases, making up about 0.0018% of the Earth's atmosphere. XENON is a colorless, odorless gas that is the least abundant of the rare gases, making up about 0.0000087% of the Earth's atmosphere.