wiki Word: noble gas

Definition:  The elements of Group 18 on the Periodic Table are noble gases which are the least reactive elements on the table.

The reactivity (or, un-reactivity should I say) of noble gases is ultimately the effect of the number of electrons located in the outer valence shell of the atom. If the outer valence shell of an atom is need of any, or needs to lose any electrons, it prompts the atom to attempt at a balance by bonding with another atom.  The elements in the noble gas group are the only ones to have completely filled their outer valence electron shells, thus making it unnecessary for them to bond with other atoms. 

This is a picture of the noble gas helium being released from a hot spring in Yellowstone National Park:

SO WHAT?  How are noble gases relevent to everyday life?

Well, when was the last time you used a lightbulb?  Probably not so long ago.  Without even realizing it, you were using a noble gas because the element Argon (Ag) is used in filament light bulbs because it's nonreactive.  In the world of chemistry, there are innumerable amounts of uses for very nonreactive elements just for the simple reason that there are some very reactive elements that must be kept in the safe environment of nonrective ones.

Cite your sources:

 "Noble gas." Wikipedia. 10 Apr 2008 < http://en.wikipedia.org/wiki/Noble_gas>.

 "Group 18 - The Noble Gases." Chemical Data. 10 Apr 2008 <http://www.rsc.org/chemsoc/visualelements//pages/data/intro_groupviii_data.html>.

Image taken from: http://www.chemistryexplained.com/Ne-Nu/Noble-Gases.html