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Characteristics

Its appearance is almost pure white, but it readily oxidizes on exposure to air, turning black.  Radium is an alkaline earth metal that that is found in trace amounts in uranium ores.  It is extremely radioactive.  Its most stable isotope,  ²²⁶Ra, has a half-life of of 1602 years and decays into radon gas.

Marie Sklodowska & Pierre Curie

The heaviest of the alkaline earth metals, radium is intensely radioactive and resembles barium in its chemical behavior.  This metal is found in minute quantities in the uranium ore pitchblende, and various other uranium minerals.  Radium preparations are remarkable for maintaining themselves at a higher temperature than their surroundings, and for their radiations, which are of three kinds: alpha particles, beta particles, and gamma rays.  Radium also produces neutrons when mixed with beryllium.

When freshly prepared, pure radium metal is brilliant white, but blackens when exposed to air (probably due to nitride formation).  Radium is luminescent (giving a faint blue color), reacts violently with water and oil to form radium hydroxide and is slightly more volatile than barium.

Occurrence

Radium is a decay product of uranium and is therefore found in all uranium-bearing ores.  Radium was originally acquired from pitchblende ore from Joachimsthal, Bohemia (One metric ton of pitchblende yields 0.0001 grams of radium).  Carnotite sands in Colorado provide some of the element, but richer ores are found in the Democratic Republic of the Congo, the Great Lakes area of Canada and can also be extracted from uranium processing waste.  Large uranium deposits are located in Ontario, New Mexico, Utah, Virginia, Australia, and in other places.

Applications

Some of the practical uses of radium are derived from its radiative properties.   More recently discovered radioisotopes, such as ⁶⁰Co and ¹³⁷Cs, are replacing radium in even these limited uses because several of these are much more powerful, they are safer to handle, and that they are more concentrated.

• Formerly used in self-luminous paints for watches, nuclear panals, aircraft switches, clocks, and instrument dials.  More than 100 former watch dial painters who used their lips to shape the paintbrush died from the radiation.  Soon afterward, the adverse effects of radioactivity became widely known.  Radium was still used in dials as late as the 1950's.  Objects painted with this paint must be handled properly.   Although tritium's beta radiation is potentially dangerous if ingested, it has replaced radium in these applications.
• When mixed with beryllium it is a neutron source for physics experiments.
• Radium (usually in the form of radium chloride) is used in medicind to produce radon gas which in turn is used as a cancer treatment.
• Radium was also put in many foods for taste and as a preservative, but also exposed many people to radiation.
• ²²³Ra is currently under investigation for use in medicine as cancer treatment of bone metastasis.
• One unit for radioactivity, the non-Si curie, is based on the radioactivity of ²²⁶Ra.
• At the turn of the 20th century radium was a popular additive in products like toothpaste, hair creams, and even food items due to its supposed curative powers.   Such products soon fell out of vogue, and were prohibited by authorities in many countries, after it was discovered they could have real and serious adverse health effects.
• Spas featuring radium-rich water are still occasionally touted as beneficial, such as those in Misasa, Tottori, Japan and Radium Hot Springs, British Columbia, Canada.

Compounds

Its compounds color flames crimson carmine (rich red or crimson color with a shade of purple) and give a characteristic spectrum.  Due to its geologically short half-life and intense radioactivity, radium compounds are quite rare, occurring almost exclusively in uranium ores.

Isotopes

Radium has 33 different known isotopes, four of which are found in nature, with ²²⁶Ra being the most common. ²²³Ra, ²²⁴Ra, ²²⁶Ra and ²²⁸Ra are all generated in the decay of either U or Th.   ²²⁶Ra is a product of ²³⁸U decay, and is the longest-lived isotope of radium with a half-life of 1602 years; next longest is ²²⁸Ra, a product of ²³²Th breakdown, with a half-life of 6.7 years.

Radioactivity

The decay products of radium were known as Radium A, B, C, etc.   These are now known to be isotopes of other elements as follows:

On February 4, 1936 radium E became the first radioactive element to be made synthetically.

During the 1930s it was found that workers exposure to radium by handling luminescent paints caused serious health effects which included sores, anemia and bone cancer.   This use of radium was stopped soon afterward.  This is because radium is treated as calcium by the body, and deposited in the bones, where radioactivity degrades marrow, and can mutate bone cells. The litigation and ultimate deaths of five "Radium Girl" employees who had used radium-based luminous paints on the dials of watches and clocks had a significant impact on the formulation of occupational disease labor law.

Its decay occurs in at least seven stages; the successive main products have been studied and were called radium emanation or exradio (this is radon), radium A (polonium), radium B (lead), radium C (bismuth), etc.  The radon is a heavy gas and the later products are solids.  These products are themselves radioactive elements, each with an atomic weight a little lower than its predecessor.

Radium loses about 1% of its activity in 25 years, being transformed into elements of lower atomic weight with lead being a final product of disintegration.

The SI unit of radioactivity is the becquerel (Bq), equal to one disintegration per second.  The curie is a non-SI unit defined as that amount of radioactivity which has the same disintegration rate as 1 gram of Ra-226 (3.7 x 10¹⁰ disintegrations per second, or 37 GBq).

Handling of radium has since been blamed for Marie Curie's premature death.  The lab notebooks used by the Curies are too highly contaminated to be safely handled today.

Precautions

Radium is highly radioactive and its decay product, radon gas, is also radioactive.  Radium is over one million times more radioactive than the same mass of uranium.  Since radium is chemically similar to calcium, it has the potential to cause great harm by replacing it in bones.  Inhalation, injection, ingestion or body exposure to radium can cause cancer and other disorders.

Stored radium should be ventilated to prevent accumulation of radon.

Emitted energy from the decay of radium ionizes gases, affects photographic plates, causes sores on the skin, and produces many other detrimental effects.

(L. radius, ray) Radium was discovered in 1898 by Mme. Curie in the pitchblende or uraninite of North Bohemia, where it occurs. There is about 1 g 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 in Joachimsthal, Bohemia. The carnotite sands of Colorado furnish some radium, but richer ores are found in the Republic of Zaire and the Great Lake region of Canada. Radium is present in all uranium minerals, and could 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 and 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 luminescence, as do its slats; it decomposes in water and is somewhat 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 produce neutrons. One gram of 226Ra undergoes 3.7 x 10¹⁰ disintegrations per s. The curie is defined as that amount of radioactivity which has the same disintegration rate as 1 g of 226Ra. Twenty five isotopes are now known; radium 226, the common isotope, has a half-life of 1600 years. One gram of radium produces about 0.0001 ml (stp) of emanation, or radon gas, per day. This is purged from the radium and sealed in minute tubes, which are used in the treatment of cancer and other diseases. Radium is used in the producing of self-luminous paints, neutron sources, and in medicine for the treatment of disease. Some of the more recently discovered radioisotopes, such as 60Co, 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 1% of its activity in 25 years, being transformed into elements of lower atomic weight. Lead is a final product of disintegration. 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 maximum permissible burder in the total body for 226Ra is 7400 becquerel.

Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond

Radium was discovered by Marie Sklodowska Curie, a Polish chemist, and Pierre Curie, a French chemist, in 1898. Marie Curie obtained radium from pitchblende, a material that contains uranium, after noticing that unrefined pitchblende was more radioactive than the uranium that was separated from it. She reasoned that pitchblende must contain at least one other radioactive element. Curie needed to refine several tons of pitchblende in order to obtain tiny amounts of radium and polonium, another radioactive element discovered by Curie. One ton of uranium ore contains only about 0.14 grams of radium. Today, radium can be obtained as a byproduct of refining uranium and is usually sold as radium chloride (RaCl₂) or radium bromide (RaBr₂) and not as a pure material.

Radium's most stable isotope, radium-226, has a half-life of about 1600 years. It decays into radon-222 through alpha decay or into lead-212 by ejecting a carbon-14 nucleus.

The Curie, a unit used to describe the activity of a radioactive substance, is based on radium-226. It is equal to the number of atoms in a one gram sample of radium-226 that will decay in one second, or 37,000,000,000 decays per second.

Radium had been used to make self-luminous paints for watches, aircraft instrument dials and other instrumentation, but has largely been replaced by cobalt-60, a less dangerous radioactive source. A mixture of radium and beryllium will emit neutrons and is used as a neutron source. Radium is used to produce radon, a radioactive gas used to treat some types of cancer. A single gram of radium-226 will produce 0.000l milliliters of radon a day.

Radium is about one million times more active than uranium. The lab notebooks used by the Curies are too highly contaminated to be safely handled today.