Group 18 Elements

Ø The 18th group of the Periodic Table consists of colourless, odourless gases at room temperature.

Ø Group-18 elements constitute the last group of p-block elements and include Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) and Radon (Rn).

Ø All these are gases and chemically unreactive. They form very few compounds, because of this they are termed as noble gases.

Ø Helium is an exception as it does not have p-orbitals. All the elements in the group are gases.

Occurrence

All these gases except radon and oganesson occur in the atmosphere. Their atmospheric abundance in dry air is ~ 1% by volume of which argon is the major constituent.

Helium and sometimes neon are found in minerals of radioactive origin e.g., pitchblende, monazite, cleveite. The main commercial source of helium is natural gas.

Xenon and radon are the rarest elements of the group. Radon is obtained as a decay product of ²²⁶Ra.

+ → + 3n

Oganesson has been synthetically produced by collision of atoms and ions

Electronic configuration

Their valence shell electronic configuration is ns²np² except helium which has 1s². The properties of noble gases including their inactive nature are ascribed to their closed shell structures.