Sources

http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/p-Block_Elements/Group_18%3A_The_Noble_Gases

Boundless. “The Noble Gases (Group 18).” Boundless Chemistry. Boundless, 17 Nov. 2014. Retrieved 06 Jan. 2015 from https://www.boundless.com/chemistry/textbooks/boundless-chemistry-textbook/periodic-properties-8/variation-in-chemical-properties-70/the-noble-gases-group-18-330-1854/