8094. Radium

Nomenclature

CAS number: 7440-14-4

Description and references

Ra; at. no. 88; valence 2. Group IIA (2). Radioactive alkaline earth metal. Occurrence in earth's crust: approx 10-11% by wt. No stable nuclides. Naturally occurring isotopes: 223, actinium X (T 1/2 ll.435 days, α emitter, rel. at. mass 223.0185); 224, thorium X (T 1/2 3.66 days, α emitter, rel. at. mass 224.0202); 226 (longest-lived isotope, T 1/2 1599 years, α emitter, rel. at. mass 226.0254); 228, mesothorium I (T 1/2 5.75 years, β- emitter, rel. at. mass 228.0311). Known radioactive isotopes: 205-222, 225, 227, 229-234. 226Ra is a product of disintegration of uranium and is present in all ores contg uranium. Separated in the form of a salt by P. and M. S. Curie from the pitchblende of Joachimsthal, Bohemia: Curie et al., Compt. Rend. 127, 1215 (1898). Isoln of the element by electrolysis of an aq soln of radium chloride: Curie, Debierne, ibid. 151, 523 (1910). Production of 228Ra by disintegration of thorium (232Th) discovered in 1907 by O. Hahn in monazite residues from isolating thorium. Determn in environmental and monitoring samples: W. C. Lawrie et al., Appl. Radiat. Isot. 53, 133 (2000). Clinical evaluation in brachytherapy of tongue: J. Horiuchi et al., Int. J. Radiat. Oncol. Biol. Phys. 8, 82 (1982); M. Hoshina et al., Br. J. Radiol. 62, 59 (1989); in intracavitary radiation of uterus: D. A. Jones, R. Stout, Clin. Radiol. 37, 169 (1986). Review of radiotherapy in cervical carcinoma: P. R. Reddi et al., Obstet. Gynecol. 43, 238-247 (1974); in rectal carcinoma: Dis. Colon Rectum 29, 600-614 (1986), reprint of C. Gordon-Watson, Br. J. Surg. 17, 649-669 (1930). Comprehensive reviews: K. W. Bagnall, Chemistry of the Rare Radioelements (New York, Academic Press, 1957); Goodenough, Stenger, “Magnesium, Calcium, Strontium, Barium, and Radium” in Comprehensive Inorganic Chemistry vol. 1, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 591-664. Review of toxicology and human exposure: Toxicological Profile for Radium (PB 91-180414, 1990) 138 pp; of discovery and medical use: J.-J. Mazeron, A. Gerbaulet, Radiother. Oncol. 49, 205-216 (1998); of industrial use: D. I. Harvie, Endeavour 23, 100-105 (1999).

Properties

Brilliant, white metal; body-centered cubic structure; blackens on exposure to air. mp 700°; bp 1737°; d 5.5. One gram of radium evolves about 1000 kcal per year. Undergoes spontaneous disintegration with formation of radon. One gram of radium produces about 0.0001 ml of radon per day at normal temp and pressure. Radium is produced and used in the form of its salts: the chloride, bromide, carbonate, sulfate. Its compds closely resemble those of barium; the element itself is more volatile than barium. Radium salts impart a carmine-red color to a flame.

Derivative

Bromide.

Nomenclature

CAS number: 10031-23-9
Br2Ra; mol wt 385.83.
Br 41.42%, Ra 58.58%.

Properties

White or slightly brownish crystals. d 5.79. mp 728°. Sublimes at 900°. Sol in water. The salt of commerce is usually a mixture with barium bromide.

Derivative

Chloride.

Nomenclature

CAS number: 10025-66-8
Cl2Ra; mol wt 296.93.
Cl 23.88%, Ra 76.12%.

Properties

White or slightly brownish crystals. d 4.91. mp 1000°. Sol in water. The salt of commerce is usually a mixture with barium chloride.

Caution

Potential symptoms of overexposure to radioactive emissions are anemia, cataracts, fractured teeth and cancer, esp. bone cancer (Toxicological Profile).

Use

In physical research. In radiography of metals because the penetration of gamma rays is more pronounced than that of x-rays. As source of radon. No longer used to make luminous paints.

Therapeutic Category

Antineoplastic (radiation source).

Keywords

Antineoplastic (Radiation Source)