Noble Gases

NOBLE GASES, chemical elements: helium, neon, argon, krypton, xenon, and emanation. They received their name due to their inability to enter into reactions with other elements. In 1894, the English scientists Rayleigh and Ramsay established that nitrogen obtained from air has a greater density (1 liter = 1.2572 g) than nitrogen obtained from a nitrogenous compound (1 liter = 1.2505 g). It was hypothesized that there is some heavier gas in the air. To isolate this gas, atmospheric nitrogen was passed repeatedly over heated magnesium, which reacted with it and turned into magnesium nitride; in the residue, a gas heavier than nitrogen was obtained; it was named inactive: argon (see). In 1895, Ramsay, while investigating a gas that is released from the mineral cleveite when heated with acids or when fused with carbonate alkalis, found in the spectrum of this gas a line identical to the line that Lockyer observed during the solar eclipse of October 20, 1868. This line was attributed to a new element, which received the name helium (sun). In 1898, Ramsay and Travers, during the fractional distillation of liquid argon, isolated three more new gaseous elements: krypton (hidden), neon (new), and xenon (strange). The sixth element of the noble gases group is a radioactive gas released by radioactive substances—emanation. Besides atmospheric air, noble gases are found, but always in very small quantities, in some minerals, in rainwater, and in the water of some mineral springs, and in gases released during volcanic eruptions. Traces of argon have also been found in blood gases. All elements of this group are colorless, tasteless, and odorless gases with a peculiar spectrum; all of them, as the determination of specific heat and the ratio (Cp : Cv) has shown, have a molecule consisting of one atom. Chemically, noble gases are completely inactive, which indicates the particular stability of their outer electrons, although very recently, compounds with water—hydrates—have been obtained for argon, krypton, and xenon. Furthermore, the latest work points to the possibility of the existence of compounds of helium with mercury, iodine, phosphorus, and tungsten, so-called helides. When comparing the properties of these elements, one can see the same sequence in the course of their changes as is observed in elements belonging to the same group of the periodic system. On this basis, at the suggestion of Ramsay, the noble gases were united into one group, called the "zero" group. Noble gases are discovered exclusively by means of spectral analysis, except for emanation, which can be detected by other methods as well. Helium and emanation have practical application, mainly. The former serves for obtaining low temperatures, is used in the manufacture of the main instrument for measuring low temperatures—the gas thermometer, for filling aerostats, etc. One of the isotopes of the latter, namely, radium emanation, currently has great application in therapy. Noble Gases | Symbol | Atomic Weight | Density | Boiling Point | Melting Point. Helium | He | 4.00 | 1.98 | -268.8 | -. Neon | Ne | 20.2 | 10.02 | -245.9 | -248.7. Argon | Ar | 39.88 | 19.96 | -185.8 | -190. Krypton | Kr | 82.9 | 40.88 | -151.7 | -169. Xenon | Xe | 130.2 | 64.6 | -106.9 | -140. Emanation | Em | - | 62 | 1 | -.