   #copyright

Radium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


               88               francium ← radium → actinium
               Ba
               ↑
               Ra
               ↓
               Ubn

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                       Name, Symbol, Number radium, Ra, 88
                                     Chemical series alkaline earth metals
                                              Group, Period, Block 2, 7, s
                                         Appearance silvery white metallic
                                                   Atomic mass (226) g/mol
                                          Electron configuration [Rn] 7s^2
                                Electrons per shell 2, 8, 18, 32, 18, 8, 2
                                                       Physical properties
                                                               Phase solid
                                        Density (near r.t.) 5.5 g·cm^−3
                                                      Melting point 973  K
                                                     (700 ° C, 1292 ° F)
                                                      Boiling point 2010 K
                                                    (1737 ° C, 3159 ° F)
                                           Heat of fusion 8.5 kJ·mol^−1
                                     Heat of vaporization 113 kJ·mol^−1

   CAPTION: Vapor pressure

                                        P/Pa   1  10  100  1 k  10 k 100 k
                                       at T/K 819 906 1037 1209 1446 1799

                                                         Atomic properties
                                     Crystal structure cubic body centered
                                                        Oxidation states 2
                                                    (strongly basic oxide)
                                     Electronegativity 0.9 (Pauling scale)
                                     Ionization energies 1st: 509.3 kJ/mol
                                                         2nd: 979.0 kJ/mol
                                                      Atomic radius 215 pm
                                                             Miscellaneous
                                             Magnetic ordering nonmagnetic
                                 Electrical resistivity (20 °C) 1 µΩ·m
                       Thermal conductivity (300 K) 18.6 W·m^−1·K^−1
                                             CAS registry number 7440-14-4
                                                         Selected isotopes

                  CAPTION: Main article: Isotopes of radium

                             iso    NA   half-life   DM   DE ( MeV)   DP
                            ^223Ra  ?    11.43 d   alpha  5.99      ^219Rn
                            ^224Ra  ?    3.6319 d  alpha  5.789     ^220Rn
                            ^226Ra trace 1602 y    alpha  4.871     ^222Rn
                            ^228Ra syn   6.7 y     beta^- 0.046     ^228Ac

                                                                References

   Radium ( IPA: /ˈreɪdiəm/) is a chemical element, which has the symbol
   Ra and atomic number 88 (see the periodic table).

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

Notable characteristics

   The heaviest of the alkaline earth metals, radium is intensely
   radioactive and resembles barium in its chemical behaviour. 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 colour), reacts violently
   with water to form radium hydroxide and is slightly more volatile than
   barium.

Applications

   Some of the practical uses of radium are derived from its radiative
   properties. More recently discovered radioisotopes, such as cobalt-60
   and caesium-137, are replacing radium in even these limited uses
   because several of these are much more powerful and others are safer to
   handle.
     * Formerly used in self-luminous paints for watches, 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 may still be dangerous, and
       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 medicine
       to produce radon gas which in turn is used as a cancer treatment.
     * Radium was also put in many foods for taste and a preservative, but
       also exposed many people to radiation
     * Radium-223 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 radium-226 (see Radioactivity).
     * 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.
       (See for instance Radithor.)
     * Spas featuring radium-rich water are still occasionally touted as
       beneficial, such as those in Misasa, Tottori, Japan.

History

   Radium (Latin radius, ray) was discovered by Maria Skłodowska-Curie and
   her husband Pierre in 1898 in pitchblende/ uraninite from North Bohemia
   (area around Jáchymov). While studying pitchblende the Curies removed
   uranium from it and found that the remaining material was still
   radioactive. They then separated out a radioactive mixture mostly
   consisting of barium which gave a brilliant red flame colour and
   spectral lines which had never been documented before. In 1902 radium
   was isolated into its pure metal by Curie and Andre Debierne through
   the electrolysis of a pure radium chloride solution by using a mercury
   cathode and distilling in an atmosphere of hydrogen gas.

   Historically 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:

          Radium emanation - radon-222
          Radium A - polonium-218
          Radium B - lead-214
          Radium C - bismuth-214
          Radium C[1] - polonium-214
          Radium C[2] - thallium-210
          Radium D - lead-210
          Radium E - bismuth-210
          Radium F - polonium 210

   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, anaemia 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. Handling of radium has since been blamed for
   Marie Curie's premature death.

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.

Compounds

   Its compounds colour flames crimson carmine (rich red or crimson colour
   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 (Ra F[2])
     * radium chloride (RaCl[2])
     * radium bromide (RaBr[2])
     * radium iodide (RaI[2])
     * radium oxide (RaO)

Isotopes

   Radium has 25 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

   Radium is over one million times more radioactive than the same mass of
   uranium. 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 10^10 disintegrations per second, or 37 GBq).

Precautions

   Radium is highly radioactive and its decay product, radon gas, is also
   radioactive. 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.

   Retrieved from " http://en.wikipedia.org/wiki/Radium"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
