Radium, emanation rays from

Element 86, the final member of the group, is a short-lived, radioactive element, formerly known as radium-emanation or niton or, depending on which radioactive series it originates in (i.e. which isotope) as radon, thoron, or actinon. It was first isolated and studied in 1902 by E. Rutherford and F. Soddy and is now universally known as radon (from radium and the termination-on adopted for the noble gases Latin radius, ray). 

M. d Arsonval, a member of the Academy of Sciences, has just presented a lecture before said Academy concerning the discovery of rays emanating from the human body and made visible by means of radium lighting [lumiere du radium]. Two researchers from the city of Nancy, Messers Charpentier and Blondlot, are the first who have used this procedure to perceive these rays, which they have called N after the initial letter of the word Nancy. Blondlot recounts how, while making a study of X-rays, they began to notice the emission of other rays which... 

In today s parlance, we call the radium emanation radon-222. (Like radium, the word radon comes from the Latin radius, for ray or beam. ) The alpha decay of radium-226 produces radon-222 and helium-4. The thorium emanation is radon-220, but the decay scheme from thorium-232 is more involved (see Problem 19.11). Rn-222 and Rn-220 are the two longest-lived isotopes of radon, the heaviest and rarest of the noble gases. (There are now 36 known isotopes of radon with mass numbers ranging from 193 to 228.) For many years, Dorn was generally credited as the sole discoverer of radon. However, as noted above, Ernest Rutherford and his co-workers, particularly Frederick Soddy, should be given at least equal billing. 

Recent discoveries would appear to suggest that this mysterious Fire of Life, which, whatever else it may have been, was evidently a force and no true fire, since it did not burn, owed its origin to the emanations from radium, or some kindred substance. Although in the year 1885, Mr. Holly would have known nothing of the properties of these marvelous rays or emanations, doubtless Ayesha was familiar with them and their enormous possibilities, of which our chemists and scientific men have, at present, but explored the fringe. (1905, 167)... 

A radioactive element is an element that disintegrates spontaneously with the emission of various rays and particles. Most commonly, the term denotes radioactive elements such as radium, radon (emanation), thorium, promethium, uranium, which occupy a definite place in the periodic table because of their atomic number. The term radioactive element is also applied to the various other nuclear species, (which arc produced by the disintegration of radium, uranium, etc.) including (he members of the uranium, actinium, thorium, and neptunium families of radioactive elements, which differ markedly in their stability, and are isotopes of elements from thallium (atomic number 81) to uranium (atomic number... 

I see his quiet research room at the top of the physics building, under the roof, where his radium was kept and in which so much well-known work on the emanation was carried out. But I also see the gloomy cellar in which he had fitted up his delicate apparatus for the study of the alpha rays. Rutherford loved this room. One went down two steps and then heard from the darkness Rutherford s voice reminding one that a hot-pipe crossed the room at head-level, and to step over two water-pipes. Then finally, in the feeble light one saw the great man himself seated at his apparatus. 

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