Spectrum = gas discharge tubes: the noble gases: helium He, neon Ne, argon Ar, krypton Kr, xenon Xe. Used with 1,8kV, 18mA, 35kHz. ≈8″ length. (Photo credit: Wikipedia)
After the Civil war, research could be done on common Chemistry rather than weapons. And I mean using the elemnts to make electric lights and better soap, not Atomic bombs and chlorine gas. So it was during the breath between wars that some scientists were looking at the chronology of the sun and discovered the spectrum of a new element; Helium. Dmitri Mendeleev, creator of the periodic table, claimed that it did not exist, because it did not fit into any of the columns on the table.
In 1895, a man named Lord Raleigh discovered that the Nitrogen taken from the air (after the Oxygen was separated, of course) was more dense than the Nitrogen taken from chemical reactions, and so concluded that there was another gas in the air. Following this discovery, an experiment was made that successfully isolated a new Element: Argon, after the Greek word Argos, or in-reactive. Dmitri Mendeleev denied the existence of this Element as well.
William Ramsay, who helped Raleigh isolate Argon, theorized that there must be a whole column of undiscovered Elements, and soon after discovered the Elements Krypton, Neon, and Xenon, after the Greek words Kryptos, (“hidden”) Neos, (“new”) and Xenos, (“stranger”). Finally, Dmitri Mendeleev accepted the evidence of these Elements, and added a new column to the periodic table, the Noble Gases.
The Noble Gases are so called because they do not not react very much with other Elements, and so they are the Noble bunch (kind of different from the Alkali group: they explode if you throw them in water). Another interesting fact about the Noble Gases is that if you run an electrical current through them, they glow. This is used extensively in shopping signs; the red ones are Neon, and the blue ones are Krypton. The above photo shows all the Noble Gases: Helium, Neon, Argon, Krypton, and Xenon.