   #copyright

Actinium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


               89                radium ← actinium → thorium
               La
               ↑
               Ac
               ↓
               Ute

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                     Name, Symbol, Number actinium, Ac, 89
                                                 Chemical series actinides
                                              Group, Period, Block 3, 7, f
                                                        Appearance silvery
                                                   Atomic mass (227) g/mol
                                     Electron configuration [Rn] 6d^1 7s^2
                                Electrons per shell 2, 8, 18, 32, 18, 9, 2
                                                       Physical properties
                                                               Phase solid
                                         Density (near r.t.) 10 g·cm^−3
                                             Melting point (circa) 1323  K
                                                    (1050 ° C, 1922 ° F)
                                                      Boiling point 3471 K
                                                    (3198 ° C, 5788 ° F)
                                            Heat of fusion 14 kJ·mol^−1
                                     Heat of vaporization 400 kJ·mol^−1
                           Heat capacity (25 °C) 27.2 J·mol^−1·K^−1
                                                         Atomic properties
                                     Crystal structure cubic face centered
                                                        Oxidation states 3
                                                           (neutral oxide)
                                     Electronegativity 1.1 (Pauling scale)
                                       Ionization energies 1st: 499 kJ/mol
                                                          2nd: 1170 kJ/mol
                                                      Atomic radius 195 pm
                                                             Miscellaneous
                                                 Magnetic ordering no data
                         Thermal conductivity (300 K) 12 W·m^−1·K^−1
                                             CAS registry number 7440-34-8
                                                         Selected isotopes

   CAPTION: Main article: Isotopes of actinium

                              iso    NA   half-life   DM  DE ( MeV)   DP
                             ^225Ac syn  10 days      α   5.935     ^221Fr
                             ^226Ac syn  29.37 hours  β^- 1.117     ^226Th
                                                      ε   0.640     ^226Ra
                                                      α   5.536     ^222Fr
                             ^227Ac 100% 21.773 years β^- 0.045     ^227Th
                                                      α   5.042     ^223Fr

                                                                References

   Actinium ( IPA: /akˈtɪniəm/) is a chemical element in the periodic
   table that has the symbol Ac and atomic number 89.

Notable characteristics

   Actinium is a silvery radioactive metallic element. Due to its intense
   radioactivity, Actinium glows in the dark with a pale blue light. It is
   found only in traces in uranium ores as ^227Ac, an α and β emitter with
   a half-life of 21.773 years. One ton of uranium ore contains about a
   tenth of a gram of actinium.

Applications

   It is about 150 times as radioactive as radium, making it valuable as a
   neutron source. Otherwise it has no significant industrial
   applications.

   ^225Ac is used in medicine to produce ^213Bi in a reusable generator or
   can be used alone as an agent for radio-immunotherapy.

History

   Actinium was discovered in 1899 by André-Louis Debierne, a French
   chemist, who separated it from pitchblende. Friedrich Otto Giesel
   independently discovered actinium in 1902. The chemical behaviour of
   actinium is similar to that of the rare earth lanthanum.

   The word actinium comes from the Greek aktis, aktinos, meaning beam or
   ray.

Occurrence

   Actinium is found in trace amounts in uranium ore, but more commonly is
   made in milligram amounts by the neutron irradiation of ^226Ra in a
   nuclear reactor. Actinium metal has been prepared by the reduction of
   actinium fluoride with lithium vapor at about 1100 to 1300ºC.

Isotopes

   Naturally occurring actinium is composed of 1 radioactive isotope;
   ^227Ac. 36 radioisotopes have been characterized with the most stable
   being ^227Ac with a half-life of 21.772 y, ^225Ac with a half-life of
   10.0 days, and ^226Ac with a half-life of 29.37 h. All of the remaining
   radioactive isotopes have half-lifes that are less than 10 hours and
   the majority of these have half lifes that are less than 1 minute. The
   shortest-lived isotope of actinium is ^217Ac which decays through alpha
   decay and electron capture. It has a half-life of 69 ns. Actinium also
   has 2 meta states.

   Purified ^227Ac comes into equilibrium with its decay products at the
   end of 185 days, and then decays according to its 21.773-year
   half-life.

   The isotopes of actinium range in atomic weight from 206 amu (^206Ac)
   to 236 amu (^236Ac).

Precautions

   ^227Ac is extremely radioactive, and in terms of its potential for
   radiation induced health effects, ^227Ac is even more dangerous than
   plutonium. Ingesting even small amounts of ^227Ac would present a
   serious health hazard.
   Retrieved from " http://en.wikipedia.org/wiki/Actinium"
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