But in Linus Pauling suggested that compounds of the noble gases should be possible. Compounds of most of the noble gases have now been found. They established their monatomic and unreactive nature. With the advent of the Rutherford-Bohr atom , electron configurations of these unreactive monatomic elements soon came to have a central role in the emerging electronic theories of chemical bonding. In their papers, both G. Lewis and W. Kossel pointed to the electron configurations of these elements as especially stable.
In each theory, the chemical properties of atoms of other elements were tied to the gain or loss of electrons from the configuration of the nearest monatomic gas. So successful were these theories in accounting for a wide range of chemical properties of the elements that the monatomic-gas electron configurations came to be thought of as chemically inviolate. This was fostered by early failures to make compounds of the gases including an attempt by Henri Moissan to prepare an argon fluoride in Nevertheless, in his classic paper, Kossel made an astute observation relevant to the chemical reactivity of these elements.
On the basis of the first ionization potentials of the gases, Kossel noted that xenon was most likely to have the capability of forming fluorides and oxides. He also allowed that a krypton fluoride might be made. Similar predictions were made later, by Andreas von Antropoff and by Linus C. Pauling , based on chemical trends in the periodic table.
These predictions led D. Yost with student A. Kaye to attempt in a xenon fluoride synthesis. That attempt failed. So matters rested until Later in , Howard H. Claasen, Henry Selig, and John G.
Even the highly unstable tetrahedral tetroxide XeO 4 was made J. Houston, A fluoride of krypton, prepared and correctly identified as KrF 2 George C. Pimentel and J. Turner, , was first reported as KrF 4 Aristid V. Grosse and coworkers, , but no compound above Kr II has ever been established. Although the easier ionization of radon leads one to expect the most extensive chemistry for that element, the high instability of even the most stable isotope has severely limited studies of it. Ramsay initially dealt with pyridine bases; in he developed a synthesis of pyridine from hydrogen cyanide prussic acid and acetylene.
From he turned to physical chemistry. This was followed by investigations into the dissociation of metal hydroxides and the determination of the specific gravity at boiling point. First, he used new methods to determine the specific gravity of a substance at boiling point, the atomic weight of metals and the surface tension of liquids up to their critical point.
From Ramsay turned his attention to the vapor pressure lines of organic and inorganic substances. He discovered that the gas pressure at constant volume is proportional to the temperature.
In , Lord Rayleigh had reported that atmospheric nitrogen and chemically synthesized nitrogen had different densities. Ramsay concluded that the air should contain another gas with a higher density. Based on the specific heat at constant volume and pressure , he concluded that the gas should be monatomic.
He called the completely unreactive gas argon. The German mineralogist William Hillebrand had discovered another unreactive gas in rocks, more precisely in uranium ores. He could not identify it, and for a century it was forgotten. Rayleigh and Ramsay agreed to pursue this gas together, and Ramsay isolated it by passing atmospheric nitrogen over red-hot magnesium to form magnesium nitride.
Following a preliminary report at the British Association meeting, Rayleigh and Ramsay announced the discovery of a new element to the Royal Society in January Although spectroscopic analysis by William Crookes confirmed that the new gas had a distinctive line-pattern, some critics disputed its elementary status.
Ramsay ignored them, and was soon pursuing another mystery gas. In February the British mineralogist Henry Miers alerted Ramsay to an unusual property of cleveite a mineral consisting mainly of uranium dioxide.
William Hillebrand — a chemist with the United States Geological Survey — had noticed that heating cleveite with sulfuric acid generated an unreactive gas, which he presumed was nitrogen. Within a week, Crookes confirmed that it was helium, an element identified spectroscopically in the sun in , but previously undetected on earth. Ramsay, however, battled on. Its vapour density relative to that of hydrogen was But the ratio of its two specific heats — at constant pressure, and at constant volume — implied that the gas was monatomic.
This gave argon an atomic weight higher than its neighbour, potassium, and hence a somewhat incongruous position in the periodic table. Two other pairs of adjacent elements — tellurium and iodine, and cobalt and nickel — were similarly misplaced in the table. Instead, they argued that the new gas was an allotrope of nitrogen, with the formula N 3. But meanwhile, the onus remained on Ramsay to justify his claims.
To confirm the status of argon and helium — and to isolate any further atmospheric gases — Ramsay needed large-scale facilities for liquefying and fractionally distilling air. Instead, Ramsay turned to William Hampson with whom Dewar was also in dispute. Hampson was an Oxford classics graduate who trained as a barrister before emerging as a scientist.
Hampson provided advice, and some liquid air, but Ramsay and his assistant Morris Travers built their own distillation apparatus — much of it improvised from recycled equipment.
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