The rare gases, also known as the noble gases, are a group of six gaseous elements found in small amounts in the atmosphere: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Collectively, they make up about 1% of the earth's atmosphere. They were discovered by scientists around the turn of the century, and because they were so unreactive, they were initially called the inert gases.

Helium was the first of the rare gases to be discovered. In fact, its discovery is unique among the elements since it is the only element to be first identified in another part of the solar system before being discovered on earth. In 1868, Pierre Janssen (1824-1907), a French astronomer, was observing a total solar eclipse from India. Janssen used an instrument called a spectroscope to analyze the sunlight. The spectroscope broke the sunlight into lines that were...