   #copyright

Promethium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                61            neodymium ← promethium → samarium
                 -
                ↑
                Pm
                ↓
                Np

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                   Name, Symbol, Number promethium, Pm, 61
                                               Chemical series lanthanides
                                            Group, Period, Block n/a, 6, f
                                                       Appearance metallic
                                               Atomic mass [145] (0) g/mol
                                     Electron configuration [Xe] 4f^5 6s^2
                                    Electrons per shell 2, 8, 18, 23, 8, 2
                                                       Physical properties
                                                               Phase solid
                                       Density (near r.t.) 7.26 g·cm^−3
                                                     Melting point 1315  K
                                                    (1042 ° C, 1908 ° F)
                                                      Boiling point 3273 K
                                                    (3000 ° C, 5432 ° F)
                                          Heat of fusion 7.13 kJ·mol^−1
                                     Heat of vaporization 289 kJ·mol^−1
                                                         Atomic properties
                                               Crystal structure hexagonal
                                                        Oxidation states 3
                                                      (mildly basic oxide)
                                 Electronegativity  ? 1.13 (Pauling scale)
                                                       Ionization energies
                                             ( more) 1st: 540 kJ·mol^−1
                                                    2nd: 1050 kJ·mol^−1
                                                    3rd: 2150 kJ·mol^−1
                                                      Atomic radius 185 pm
                                              Atomic radius (calc.) 205 pm
                                                             Miscellaneous
                                                 Magnetic ordering no data
                          Electrical resistivity ( r.t.) est. 0.75 µΩ·m
                       Thermal conductivity (300 K) 17.9 W·m^−1·K^−1
                                      Thermal expansion ( r.t.) (α, poly)
                                                        est. 11 µm/(m·K)
                                     Young's modulus (α form) est. 46 GPa
                                       Shear modulus (α form) est. 18 GPa
                                        Bulk modulus (α form) est. 33 GPa
                                         Poisson ratio (α form) est. 0.28
                                             CAS registry number 7440-12-2
                                                         Selected isotopes

   CAPTION: Main article: Isotopes of promethium

                                  iso   NA  half-life DM  DE ( MeV)   DP
                                 ^145Pm syn 17.7 y    ε   0.163     ^145Nd
                                 ^146Pm syn 5.53 y    ε   1.472     ^146Nd
                                                      β^- 1.542     ^146Sm
                                 ^147Pm syn 2.6234 y  β^- 0.224     ^147Sm

                                                                References

   Promethium ( IPA: /prə(ʊ)ˈmiːθiəm/) is a chemical element in the
   periodic table that has the symbol Pm and atomic number 61.

Notable characteristics

   Promethium has one semi-stable isotope (145), it is a soft beta
   emitter; it does not emit gamma rays, but beta particles impinging on
   elements of high atomic numbers can generate X-rays. Pure promethium
   exists in two allotropic forms, and its chemistry is similar to other
   lanthanides. Promethium salts luminesce in the dark with a pale blue or
   greenish glow due to their high radioactivity. Promethium can be found
   in traces in some uranium ores as a fission product.

Applications

   Uses for promethium include:
     * Beta radiation source for thickness gauges.
     * Light source for signals that require reliable, independent
       operation (using phosphor to absorb the beta radiation and produce
       light).
     * In a nuclear battery in which photocells convert the light into
       electric current, yielding a useful life of about five years using
       147-Pm.
     * Possibly in the future as a portable X-ray source, as an auxiliary
       heat or power source for space probes and satellites.

History

   The existence of promethium was first predicted by Bohuslav Brauner in
   1902; this prediction was supported by Henry Moseley in 1914, who found
   a gap for a missing element which would have atomic number 61, but was
   unknown (however, Moseley of course had no sample of the element to
   verify this). Several groups claimed to have produced the element, but
   they could not confirm their discoveries because of the difficulty of
   separating promethium from other elements. Proof of the existence of
   promethium was obtained in 1945 by Jacob A. Marinsky, Lawrence E.
   Glendenin and Charles D. Coryell during the analysis of byproducts of
   uranium fission; however, being too busy with defense-related research
   during World War II, they did not announce their discovery until 1947.
   The name promethium is derived from Prometheus in Greek mythology, who
   stole the fire of the sky and gave it to mankind. The name was
   suggested by Grace Mary Coryell, Charles Coryell's wife, who felt that
   they were stealing fire from the gods.

   In 1963, ion-exchange methods were used to prepare about 10 grams of
   promethium from atomic reactor fuel processing wastes.

   Today, promethium is still recovered from the byproducts of uranium
   fission; it can also be produced by bombarding ^146Nd with neutrons,
   turning it into ^147Nd which decays into ^147Pm through beta decay with
   a half-life of 11 days.

Occurrence

   Promethium can be formed as a product of uranium fission. Only trace
   amounts can be found in naturally occurring ores: a sample of
   pitchblende has been found to contain promethium at a concentration of
   four parts per quintillion (10^18) by mass.

   Promethium has also been identified in the spectrum of the star HR 465
   in Andromeda, and possibly HD 101065 ( Przybylski's star) and HD 965.

Compounds

   Promethium compounds include:
     * Chlorides
          + PmCl[3]
     * Bromides
          + PmBr[3]
     * Oxides
          + Pm[2]O[3]

Isotopes

   36 radioisotopes of promethium have been characterized, with the most
   stable being ^145Pm with a half-life of 17.7 years, ^146Pm with a
   half-life of 5.53 years, and ^147Pm with a half-life of 2.6234 years.
   All of the remaining radioactive isotopes have half-lives that are less
   than 364 days, and the majority of these have half lives that are less
   than 27 seconds. This element also has 11 meta states with the most
   stable being ^148Pm^m (T[½] 41.29 days), ^152Pm^m2 (T[½] 13.8 minutes)
   and ^152Pm^m (T[½] 7.52 minutes).

   The isotopes of promethium range in atomic weight from 127.9482600 u
   (^128Pm) to 162.9535200 u (^163Pm). The primary decay mode before the
   longest-lived isotope, ^145Pm, is electron capture, and the primary
   mode after is beta minus decay. The primary decay products before
   ^145Pm are neodymium (Nd) isotopes and the primary products after are
   samarium (Sm) isotopes.

Precautions

   Promethium must be handled with great care because of its high
   radioactivity. In particular, promethium can emit X-rays during its
   beta decay. Note that its half-life is less than that of plutonium-239
   by a factor of multiple thousands to tens of thousands. Promethium has
   no biological role.
   Retrieved from " http://en.wikipedia.org/wiki/Promethium"
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   with only minor checks and changes (see www.wikipedia.org for details
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