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H' at. wt. (natural) 1.007967
   at. wt. (H') 1.007822
   at. no. 1
   m.p. - 259.140C
   b.p. - 252.870C 
   density 0.08988 gm./l
   density (liquid) 70.8 gm/i. (-2530C)
   density (solid) 7016 gm/i. (-2620C)
   valence 1.

**Electronic configuration**
K	L	M	N	O	P	Q
1	2	3	4	5	6	7
s	s p	s p d	s p d f	s p d f	s p d f	s p d f
1

RADIUM (L. radius, ray) Ra; at. wt. (226); at. no.88; m.p. 7000C; b.p. 11400C;sp. gr. 5?; valence 2. Radium was discovered in 1898 by M. and Mme. Curie in the pitchblende or uraninite of North Bohemia, in which it occurs. There is about I Isni. of radium in 7 tons of pitchblende: The element was isolated in 1911 by Mme. Curie and Debierne by the electrolysis of a solution of pure radium chloride, employing a mercury cathode; on distillation in an atmosphere of hydrogen this amalgam yielded the pure metal. Originally, radium was obtained from the rich pitchblende ore found at Joachimsthal, Bohemia. The carnotite sands of Colorado furnish some radium, but richer ores are found in the Democratic Republic of Congo and the Great Bear Lake region of Canada. Radium is present in all uranium minerals, andcould be extracted, if desired, from the extensive wastes of uranium processing. Large uranium deposits are located in Ontario, New Mexico, Utah, Australia, and elsewhere. Radium is obtained commercially as the bromide or chloride; it is doubtful if any appreciable stock of the isolated element now exists. The pure metal is brilliant white when freshly prepared, but blackens on exposure to air, probably due to formation of the nitride. It exhibits lumi- nescence, as do its salts; it decomposes in water and is some- what more volatile than barium. It is a member of the alkaline-earth group of metals. Radium imparts a carmine red color to a flame. Radium emits alpha, beta, and gamma rays and when mixed with beryllium produces neutrons. One gram of Ra226 undergoes 3.7 x 1010 disintegrating per sec The curie is defined as that amount of radioactivity which has the same disintegration rate as 1 gm. of Ra226. Sixteen isotopes are now known; radium-226, the common isotope, has a half-life of 1620 yrs. One gram of radium produces about 0.0001 milliliter (stp) of elnanation, or radon gas, per day. This is pumped from the radium and sealed in minute tubes, which are used in the treatment of cancer and other diseases. One gram of radium yields about 1000 calories per year. Radium is used in producing self-luminous paints, neutron sources and in medicine for the treatment of disease. Some of the more recently discovered radio- isotopes, such as Co60, are now being used in place of radium. Some of these sources are much more powerful, and others are safer to use. Radium loses about I % of its activity in 25 yrs., being transformed into elements of lower atomic weight. Lead is a final product of disintegra- tion. The study of radium has greatly altered our ideas of the structure of the atom. Radium is a radiological hazard. (Stored radium should be ventilated to prevent build-up of radon.) Inhalation, injection, or body exposure to radium can cause cancer and other body disorders. The recom- mended maximum allowable concentration for total body content is 0.1 microgram and exposure to 2 roentgens/mo. Radium in the form of the chloride or btomide is available without A.E.C. permit at a cost of about $25 to $50/milli- gram, plus service charges.

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