![]() Prior to Bartlett ’s preparation of the first xenon compound, the rare gases were widely referred to as the inert gases. The reactivity of any element is due, in part, to how easily it gains or loses electrons, which is necessary for an atom to react with other atoms. The configuration of electrons in these elements makes them very stable and therefore unreactive. The low reactivity of the rare gases is due to the arrangement of electrons in the rare gas atoms. Because some rare gas compounds have powerful oxidizing properties (they can remove electrons from other substances) they have been used to synthesize other compounds. Krypton and radon have also been combined with fluorine to form simple compounds. ![]() Since then, many xenon compounds containing mostly fluorine or oxygen atoms have also been prepared. In 1962, English-born American chemist Neil Bartlett (1932 –), then at the University of British Columbia, succeeded in the historic preparation of the first compound of xenon. Helium, neon, and argon do not combine with any other atoms to form compounds, and it has been only in the last few decades that compounds of the other rare gases have been prepared. The most noticeable feature of the rare gases is their lack of chemical reactivity. They are also monatomic gases which means that they exist as individual atoms. The rare gases are all colorless, odorless, and tasteless. As with other groups of elements, the placement of all the rare gases in the same group reflects their similar properties. This is the vertical column of elements on the extreme right of the periodic table. The rare gases form group 18 of the periodic table of elements. Ramsay and Rayleigh received Nobel Prizes in 1904 for their scientific contributions in discovering and characterizing the rare gases. Radon, which is radioactive, was first detected as a gas released from radium and, subsequently, identified in air. The names given to the new elements were derived from Greek words that reflected the difficultly in isolating them: Ne, neos (new) Ar, argos (inactive) Kr, kryptos (hidden) Xe, xenon (stranger). The method used to isolate these new gaseous elements involved liquefying air (by subjecting it to high pressure and low temperature) and allowing the various gases to boil off at different temperatures. Eventually it was realized that there were several new gases in the air. Ramsay eventually concluded that the nitrogen obtained from chemical reactions was pure, but nitrogen extracted from the air contained small amounts of an unknown gas which accounted for the density discrepancy. ![]() Nitrogen obtained from the air (after removal of oxygen, carbon dioxide, and water vapor) always had a slightly higher density than when prepared from a chemical reaction (such as heating certain nitrogen-containing compounds). Beginning in 1893, Rayleigh observed discrepancies in the density of nitrogen obtained from different sources. The discovery of the remaining rare gases is credited to two men, Ramsay and Lord Rayleigh (1842 – 1919). Shortly thereafter, helium was also detected as a minor component in Earth ’s atmosphere. ![]() ![]() With help from two British experts on spectroscopy, William Crooks (1832 –1919) and Norman Lockyer (1836 –1920), the presence of helium in Earth-bound minerals was confirmed. A quarter of a century later, Scottish chemist and physicist William Ramsay (1852 –1916) studied gases emitted from radioactive uranium ores. He saw a previously unobserved line in the solar spectrum, which indicated the presence of a new element that Janssen named helium after the Greek word helios, meaning sun. The spectroscope broke the sunlight into lines which were characteristic of the elements emitting the light. Janssen used an instrument called a spectroscope to analyze the sunlight. In 1868, Pierre Janssen (1824 –1907), a French astronomer, was observing a total solar eclipse from India. 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 the Earth. Helium was the first of the rare gases to be discovered. Although rare gases is used often to describe these elements, they are only rare in abundance relative to other gases found in the atmosphere of Earth. They were discovered by scientists near the end of the nineteenth century, and because they were so unreactive were initially called the inert gases. Collectively they make up about one percent of Earth ’s atmosphere. The rare gases, also known as the noble gases or the inert 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). ![]()
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