At room temperature, there are 11 gaseous elements in the peridoic table. Among these, 6 elements with similiar chemical and physical properties are the group 8A elements. These elements are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). They are also called noble gases or inert gases.
Occur
These elements are colorless, monoatomic gases. They exist in trace amount in air. Argon is the most abundant noble gas in air. The abundances of the noble gases in the atmosphere are given in table 1. The nobel gases, except He and Rn, are produced by the fractional distillation of air. Helium nuclei are composed of the alpha (a) particles emitted by radioactive elements such as uranium. Helium is stored either inside magma or in wells of natural gas. Radon is obtained in small quantities from the radioactive decay of uranium.