![]() Because helium has the lowest boiling point of any substance known (4.2 K), it is used primarily as a cryogenic liquid. For their discovery of the noble gases, Rayleigh was awarded the Nobel Prize in Physics and Ramsay the Nobel Prize in Chemistry in 1904. The element was named radon (Rn), and Ramsay succeeded in obtaining enough radon in 1908 to measure its density (and thus its atomic mass). The last noble gas was discovered in 1900 by the German chemist Friedrich Dorn, who was investigating radioactivity in the air around the newly discovered radioactive elements radium and polonium. Then, in a single year (1898), he discovered the next three noble gases: krypton (Kr), from the Greek kryptos, meaning “hidden,” was identified by its orange and green emission lines neon (Ne), from the Greek neos, meaning “new,” had bright red emission lines and xenon (Xe), from the Greek xenos, meaning “strange,” had deep blue emission lines. In 1895, Ramsey was able to obtain a terrestrial sample of helium for the first time. He is best known for his work on the oxides of nitrogen and for the discovery of the noble gases with Lord Rayleigh. ![]() When he returned to England, his interests turned first to physical chemistry and then to inorganic chemistry. Ramsay earned his PhD in organic chemistry at the University of Tübingen in Germany in 1872. Instead, he became interested in chemistry while reading about the manufacture of gunpowder. He also suggested that these elements should have a preferred valence of 0, intermediate between the +1 of the alkali metals and the −1 of the halogens.īorn and educated in Glasgow, Scotland, Ramsay was expected to study for the Calvanist ministry. Because they could not force this substance to decompose or react with anything, they named it argon (Ar), from the Greek argos, meaning “lazy.” Because the measured molar mass of argon was 39.9 g/mol, Ramsay speculated that it was a member of a new group of elements located on the right side of the periodic table between the halogens and the alkali metals. ![]() In 1894, he and the Scottish chemist William Ramsay announced the isolation of a new “substance” (not necessarily a new element) from the residual nitrogen gas. Strutt (Lord Rayleigh) carefully measured the density of the gas that remained after he had removed all O 2, CO 2, and water vapor from air and showed that this residual gas was slightly denser than pure N 2 obtained by the thermal decomposition of ammonium nitrite. (For more information on spectroscopy, see Chapter 6 "The Structure of Atoms".) Actual samples of helium were not obtained until almost 30 years later, however. Helium was the first of the noble gases to be identified, when the existence of this previously unknown element on the sun was demonstrated by new spectral lines seen during a solar eclipse in 1868. Their very existence was not suspected until the 18th century, when early work on the composition of air suggested that it contained small amounts of gases in addition to oxygen, nitrogen, carbon dioxide, and water vapor. ![]() The noble gases were all isolated for the first time within a period of only five years at the end of the 19th century.
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