88
  Ra  
226.000000
Radium

Name: Radium
Symbol: Ra
Atomic Number: 88
Atomic Weight: 226.000000
Family: Alkaline Earth Metals
CAS RN: 7440-14-4
Description: An alkaline earth metal, metallic white but tarnishes black upon exposure to air.
State (25C): Solid
Oxidation states: +2

Molar Volume: 39 cm3/mole
Valence Electrons: 7s2

Boiling Point:  1809K, 1536C, 2797F
Melting Point:
973K, 700C, 1292F
Electrons Energy Level: 2, 8, 18, 32, 18, 8, 2
Isotopes: 33 + None Stable
Heat of Vaporization: unknown
Heat of Fusion: 37 kJ/mol
Density: 5.5 g/cm3 @ 300K
Specific Heat: 0.12 J/gK
Atomic Radius: unknown
Ionic Radius: 1.43
Electronegativity: 0.9 (Pauling); 1 (Allrod Rochow)
Vapor Pressure: 327 Pa @ 700C
4
Be
9.012
Radium (Latin radius, ray) was discovered by Marie Sklodowska Curie, a Polish chemist, and Pierre Curie, a French chemist, in 1898, from pitchblende, a mineral known as urannite, from North Bohemia an area around Jachymov.  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.  They then separated out a radioactive mixture mostly consisting of barium which gave a brilliant red flame color and spectral lines which had never been documented before.

Curie needed to refine several tons of this mixture 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.

In 1902 radium was isolated into its pure metal by Curie and Andre-Louis Debierne through the electrolysis of a pure radium chloride solution by using a mercury cathode and distilling in an atmosphere of hydrogen gas.

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.

12
Mg
24.30
20
Ca
40.07
38
Sr
87.62
56
Ba
137.3
88
Ra
226.0

1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10 6s2p6 7s2

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.

mpcurie.jpg (53047 bytes)

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.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d10
6s2 6p6
7s2

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.

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.

Radium Fluoride, RaF2 Radium Chloride, RaCl2
Radium Bromide, RaBr2 Radium Iodide, RaI2
Radium Oxide, RaO Radium Nitride, Ra3N2

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.

atom.gif (700 bytes)

Isotope Atomic Mass Half-Life
Ra202   0.7 ms
Ra203   1 ms
Ra204 204.006 59 ms
Ra205 205.006 210 ms
Ra206 206.004 0.24 seconds
Ra207 207.004 1.3 seconds
Ra208 208.002 1.3 seconds
Ra209 209.002 4.6 seconds
Ra210 :210.000 3.7 seconds
Ra211 211.0009 13 seconds
Ra212 211.9998 13 seconds
Ra213 213.0003 2.74 minutes
Ra214 214. 2.46 seconds
Ra215 215.0027 1.59 ms
Ra216 216.0035 182 ns
Ra217 217.0063 1.6 us
Ra218 218.0071 25.6 us
Ra219 219.0101 10 ms
Ra220 220.011 18 ms
Ra221 221.0139 28 seconds
Ra222 222.0154 38 seconds
Ra223 223.0185 11.435 days
Ra224 224.0202 3.66 days
Ra225 225.0236 14.9 days
Ra226 226.0254 1600 years
Ra227 227.0292 42.2 minutes
Ra228 228.0311 5.75 years
Ra229 229.0348 4 minutes
Ra230 230.0371 93 minutes
Ra231 231.041 103 seconds
Ra232 232.044 250 seconds
Ra233 233.048 30 seconds
Ra234 234.051 30 seconds

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:

  Isotope
Radium Emanation 222Rn
Radium A 218Po
Radium B 214Pb
Radium C 214Bi
Radium C1 214Po
Radium C2 210Tl
Radium D 210Pb
Radium E 210Bi
Radium F 210Po

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

40px-Skull_and_crossbones.svg.jpg (1420 bytes) 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.


atom.gif (700 bytes)

Radium Data

 

Atomic Structure

Atomic Radius (): unknown
Atomic Volume cm3/mol : 45.2cm3/mol
Covalent Radius: unknown
Crystal Structure: Cubic body centered
Ionic Radius: 1.43

Chemical Properties

Electrochemical Equivalents: 4.2165 g/amp-hr
Electron Work Function: unknown
Electronegativity: 0.9 (Pauling); 1 (Allrod Rochow)
Heat of Fusion: 37 kJ/mol
Incompatibilities: unknown
First Ionization Potential: 5.279
Second Ionization Potential: 10.148
Third Ionization Potential: unknown
Valence Electron Potential(-eV): 20.1
Ionization Energy (eV): 5.279 eV

Physical Properties

Atomic Mass Average: 226.0254
Boiling Point: 1809K, 1536C, 2797F
Melting Point: 973K, 700C, 1292F
Heat of Vaporization: unknown
Coefficient of Lineal Thermal Expansion/K-1: N/A
Electrical Conductivity: unknown
Thermal Conductivity: 0.186 W/cmK
Density: 5.5 g/cm3 @ 300K
Elastic Modulus (Bulk): unknown
Elastic Modulus (Rigidity): unknown
Elastic Modulus Youngs: unknown
Enthalpy of Atomization: 163 kJ/mole @ 25C
Enthalpy of Fusion: unknown
Enthalpy of Vaporization: unknown
Hardness Scale (Brinell): unknown
Hardness Scale (Mohs): unknown
Hardness Scale (Vickers): unknown
Flammability Class: unknown
Molar Volume: 39 cm3/mole
Optical Reflectivity: unknown
Optical Refractive Index: unknown
Relative Gas Density (Air=1): unknown
Specific Heat: 0.12 J/gK
Vapor Pressure: 327 Pa @ 700C
Estimated Crustal Abundance: 910-7 milligrams per kilogram
Estimated Oceanic Abundance:
8.910-11 milligrams per liter


(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.