Group — 18, The Noble Gases
Helium, Ne, Ar, Kr, Xe and Rn are noble gases and elements of group 18 (or zero group). They are minor constituents of the atmosphere. Sir William Ramse first isolated Ne, Ar, Kr and Xe. He also established He. It is found in stars, in radioactive minerals and some natural gasses. Its origin is entirely from the decay of thorium and uranium isotopes, which emit α-particles. The last member of the group Rn is radioactive (all isotopes). These gases are obtained by fractionation of liquid air.
- Ar is most abundant and Kr is least
All noble gases are monoatomic. It is due to closed-shell ...