Noble gases are a distinctive collection of elements with unique qualities that influence their behavior and interactions. This article explores their place on the periodic table, the characteristics stemming from this position, and their natural occurrence.
Position on the Periodic Table
Noble gases are located in Group 18 on the far-right side of the periodic table. This column includes Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn), and the synthetic element Oganesson (Og). Their placement signifies a complete outer electron shell. Most noble gases have eight electrons in their outermost shell, a stable arrangement known as an octet, while helium has two. This filled valence shell is the reason for their general stability and low reactivity.
Unique Properties Linked to Their Location
The full outer electron shells of noble gases contribute to their inertness and stability. Atoms with complete valence shells have minimal tendency to gain, lose, or share electrons. This means noble gases typically do not form chemical bonds with other elements under ordinary conditions. They are generally found as single atoms rather than molecules.
These elements are colorless, odorless, and tasteless gases under standard conditions. Their weak interatomic forces result in very low melting and boiling points, so they remain in a gaseous state at room temperature and pressure. While “inert gases” was historically used, modern understanding acknowledges that heavier noble gases like xenon and krypton can form compounds under specific, often extreme, conditions.
Presence in the Natural World
Noble gases are present in the natural world, though their abundance varies significantly and they are often scarcer than other elements. Helium, while abundant in the universe, is relatively rare on Earth. On our planet, helium is primarily found in natural gas deposits, formed from the radioactive decay of elements within the Earth’s crust.
Neon, Argon, Krypton, and Xenon are primarily found in Earth’s atmosphere. Argon is the most abundant noble gas in the atmosphere, making up nearly 1% of the air, and its atmospheric levels have gradually increased over geological time from the decay of potassium-40 in rocks. Neon constitutes a much smaller fraction of the atmosphere, around 0.0018%. Radon, a radioactive noble gas, is formed from the natural decay of uranium and thorium found in rocks, soil, and groundwater. These gases are typically encountered as free, uncombined atoms in their natural environments.