Radium Chemische Eigenschaften,Einsatz,Produktion Methoden
Chemische Eigenschaften
Radium (Ra) is a radioactive element, found
naturally occurring in the environment. Ra is a silvery-
white-metallic solid @ 25℃; it tarnishes black when
exposed to air. It is an alkaline earth metal; there are 33
isotopes, all of them are unstable. Radium is commonly
available as radium bromide (RaBr2 ) or radium chloride
(RaCl2 ).
Physikalische Eigenschaften
Radium is the last element in group 2 and is very similar to the other alkali earth metals,which makes it the largest and heaviest element in the group. It particularly resembles barium,which is just above it in group 2 of the periodic table. Radium is a bright white radioactiveluminescent alkali earth metal that turns black when exposed to air. Its melting point is700°C, its boiling point is 1,140°C, and its density is approximately 5.0 g/cm
3.
Isotopes
There are no stable isotopes of radium. Radium has 25 known radioisotopes,ranging from Ra-206 to Ra-230. Their half-lives range from a fraction of a second tohundreds of years. Radium-226 was discovered by the Curies and has a half-life ofabout 1630 years. Ra-226 is the most abundant isotope, and thus, Ra-226 is used todetermine radium’s atomic mass.Various radium isotopes are derived through a series of radioactive decay processes. Forexample, Ra-223 is derived from the decay of actinium. Ra-228 and Ra-224 are the resultof the series of thorium decays, and Ra-226 is a result of the decay of the uranium series.
Origin of Name
Radium’s name is derived from the Latin word radius, which means
“ray.
Occurrence
Radium is the 85th most abundant element found in the Earth’s crust. Radium is found inthe uranium ores pitchblende and chalcolite, which are both very radioactive. Radium metalexists to the extent of only one part to every three million parts of the uranium ore (pitchblende). Only about one gram of radium is found in every seven or eight tons of uraniumore. This scarcity seems to be the reason that only about five pounds of uranium are producedeach year in the entire world. Uranium ores are found in the states of Utah, New Mexico, andColorado in the United States and in Canada, the Czech Republic, Slovakia, Russia, Zaire,and France.
Charakteristisch
Radium is extremely radioactive. It glows in the dark with a faint bluish light. Radium’sradioisotopes undergo a series of four decay processes; each decay process ends with a stableisotope of lead. Radium-223 decays to Pb-207; radium-224 and radium-228decay to Pb-208;radium-226 decays to Pb-206; and radium-225 decays to Pb-209. During the decay processesthree types of radiation—alpha (α), beta (β), and gamma (γ)—are emitted.In addition to being radioactive, radium is extremely chemically reactive and forms manycompounds. These radium compounds are not only radioactive but also toxic and should behandled by experienced personnel.
Verwenden
Radium’s most important use is as a source of radiation in industry, medicine, and laboratories. The isotope radium-226, which is the most abundant of all the 25 isotopes and has ahalf-life of 1630 years, is the only useful form of the element. It is used in the medical treatment of malignant cancer growth. It kills cancer cells that have spread throughout the body.Other uses are to produce phosphorescence and fluorescence in organic compounds andfor scintillation screens on instruments used to detect radiation. Radium salts were used in thepast to paint the dials of luminous clock faces that glow in the dark.
Definition
A white radioactive luminescent metallic element of the alkaline- earth group. It has several short-lived radioisotopes and one long-lived isotope, radium-226 (half-life 1602 years). Radium is found in uranium ores, such as the oxides pitchblende and carnotite. It was formerly used in luminous paints and radiotherapy. Symbol: Ra; m.p. 700°C; b.p. 1140°C; r.d. 5 (approx. 20°C); p.n. 88; r.a.m. 226.0254 (
226Ra).
Hazard
Because radium energetically emits three types of radiation, it poses great danger to anyone handling it. In addition, it is toxic. If it is ingested in even small amounts, it replaces bone tissue, which can result in radiation sickness and death.
One of the decay products of radium is the gas radon, which can seep up through the Earth s crust into basements and slab level homes. Good ventilation assures that the radon does not accumulate to the extent that would be harmful.
At one time, women painted clock and watch dials with luminous radium paint that was a mixture of radium salts and zinc sulfide. They would place the small brushes between their lips and tongue to make the bristles more pointed, in order to paint fine lines with the radium paint. Over the years, they developed cancers that resulted in badly eaten-away and disfigured lips and jaws. Once the danger was known, luminous radium paint was banned for this use. Today, promethium (Pm-147), with a half-life of 2.4 years, is used for this purpose.
Carcinogenicity
The U.S. EPA has classified
radium as a class A carcinogen, meaning that there are
sufficient data to support a link between exposure to radium
and the development of human cancer. The α-particle radiation
associated with radium is recognized as the causative
agent for sarcomas of the bone and carcinomas of the
paranasal sinuses in humans. A study attempting to
ascertain the dose–incidence relationship for induction of
these tumors examined 1474 women employed in the U.S.
radium dial painting industry before 1930. This population
exhibited 61 known cases of bone sarcoma and 21 cases of
carcinoma of the paranasal sinuses or the mastoid air
cells. Of these individuals, the radium body burden
was known for 759, among whom there were 38 cases of bone
sarcoma and 17 head carcinomas.
Environmental Fate
Radium is released to the environment from a variety of
sources, including milling and mining operations focused on
phosphates and uranium, waste streams from factories used
to produce products containing radium, or waste byproducts
from production, such as phosphate fertilizers. The most important route of radium release into the environment is the
combustion of coal, and released radium is estimated at 150 Ci
per year (or 5.55×10
12 Bq). Radium released into the atmosphere
will remain in particulate form until wet or dry deposition.
Radium adsorbs to soils, and is not expected to volatize
from soils or water due to its ionic nature. In water, radium
exists as Ra
+2 and can interact with sediments and dissolve in
water, and therefore generally adsorbs to sediments at the
emission site and is not transported. Some isotopes of radium
are very short lived, but radium-226 has a half-life of
1600 years, making long-range transport more likely, though
generally only through an atmospheric route. Radium’s ionic
nature makes bioaccumulation or biomagnification unlikely.
Versand/Shipping
UN3323(does not appear in the 49CFR hazard
materials tables ) Radioactive material, Type C package,
nonfissile or fissile excepted. UN2915 Radioactive mate-
rial, Type A package nonspecial form, nonfissile or fissile-
excepted, Hazard class: 7-Radioactive material; Labels:
None. A1 and A2 values for Radium- 226 taken from
y173.435 (see also Table A-1 in 10CFR71(Appendix A): A1
(SpecialForm * ) 0.3 TBq (8.11Ci); A2 (NormalForm)
0.02TBq (0.541Ci))
Inkompatibilit?ten
Metallic radium is highly chemically
reactive. It forms compounds that are very similar to barium
compounds, making separation of the two elements
difficult. On contact with water, radium forms flammable
hydrogen gas.
Waste disposal
Radioactive material consid-
ered waste and must be retained in containers for disposi-
tion by the authorizing institution. Drain disposal is
prohibited. It is the responsibility of the operating institu-
tion to arrange for the proper disposal of all forms of any
radioisotopes. The use, storage, transportation, labeling,
and disposal of radioactive material are regulated through
the Nuclear Regulatory Commission (NRC) using 10 CFR
(Code of Federal Regulations) as the regulatory basis and
49 CFR (Transportation).
Radium Upstream-Materialien And Downstream Produkte
Upstream-Materialien
Downstream Produkte
