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Thulium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                69              erbium ← thulium → ytterbium
                 -
                ↑
                Tm
                ↓
                Md

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                      Name, Symbol, Number thulium, Tm, 69
                                               Chemical series lanthanides
                                            Group, Period, Block n/a, 6, f
                                                   Appearance silvery gray
                                           Atomic mass 168.93421 (2) g/mol
                                    Electron configuration [Xe] 4f^13 6s^2
                                    Electrons per shell 2, 8, 18, 31, 8, 2
                                                       Physical properties
                                                               Phase solid
                                       Density (near r.t.) 9.32 g·cm^−3
                                    Liquid density at m.p. 8.56 g·cm^−3
                                                     Melting point 1818  K
                                                    (1545 ° C, 2813 ° F)
                                                      Boiling point 2223 K
                                                    (1950 ° C, 3542 ° F)
                                         Heat of fusion 16.84 kJ·mol^−1
                                     Heat of vaporization 247 kJ·mol^−1
                          Heat capacity (25 °C) 27.03 J·mol^−1·K^−1

   CAPTION: Vapor pressure

                                   P/Pa   1    10  100  1 k   10 k  100 k
                                  at T/K 1117 1235 1381 1570 (1821) (2217)

                                                         Atomic properties
                                               Crystal structure hexagonal
                                                        Oxidation states 3
                                                            ( basic oxide)
                                    Electronegativity 1.25 (Pauling scale)
                                                       Ionization energies
                                           ( more) 1st: 596.7 kJ·mol^−1
                                                    2nd: 1160 kJ·mol^−1
                                                    3rd: 2285 kJ·mol^−1
                                                      Atomic radius 175 pm
                                              Atomic radius (calc.) 222 pm
                                                             Miscellaneous
                                                 Magnetic ordering no data
                          Electrical resistivity ( r.t.) (poly) 676 nΩ·m
                       Thermal conductivity (300 K) 16.9 W·m^−1·K^−1
                                          Thermal expansion ( r.t.) (poly)
                                                           13.3 µm/(m·K)
                                                  Young's modulus 74.0 GPa
                                                    Shear modulus 30.5 GPa
                                                     Bulk modulus 44.5 GPa
                                                       Poisson ratio 0.213
                                                  Vickers hardness 520 MPa
                                                  Brinell hardness 471 MPa
                                             CAS registry number 7440-30-4
                                                         Selected isotopes

                 CAPTION: Main article: Isotopes of thulium

                                 iso    NA  half-life DM  DE ( MeV)   DP
                                ^167Tm syn  9.25 d    ε   0.748     ^167Er
                                ^168Tm syn  93.1 d    ε   1.679     ^168Er
                                ^169Tm 100% Tm is stable with 100 neutrons
                                ^170Tm syn  128.6 d   β^- 0.968     ^170Yb
                                ^171Tm syn  1.92 y    β^- 0.096     ^171Yb

                                                                References

   Thulium ( IPA: /ˈθuːliəm/) is a chemical element that has the symbol Tm
   and atomic number 69 in the periodic table. A lanthanide element,
   thulium is the least abundant of the rare earths and its metal is easy
   to work, has a bright silvery-gray luster and can be cut by a knife. It
   also has some corrosion resistance in dry air and good ductility.
   Naturally occurring thulium is made entirely of the stable isotope
   Tm-169.

Applications

   Thulium has been used to create lasers but high production costs have
   prevented other commercial uses from being developed. Other
   applications, real and potential, include:
     * When stable thulium (Tm-169) is bombarded in a nuclear reactor it
       can later serve as a radiation source in portable x-ray devices.
     * The unstable isotope Tm-171 could possibly be used as an energy
       source.
     * Tm-169 has potential use in ceramic magnetic materials called
       ferrites, which are used in microwave equipment.

History

   Thulium was discovered by Swedish chemist Per Teodor Cleve in 1879 by
   looking for impurities in the oxides of other rare earth elements (this
   was the same method Carl Gustaf Mosander earlier used to discover some
   other rare earth elements). Cleve started by removing all of the known
   contaminants of erbia (Er[2]O[3]) and upon additional processing,
   obtained two new substances; one brown and one green. The brown
   substance turned out to be the oxide of the element holmium and was
   named holmia by Cleve and the green substance was the oxide of an
   unknown element. Cleve named the oxide thulia and its element thulium
   after Thule, Scandinavia.

Occurrence

   The element is never found in nature in pure form, but it is found in
   small quantities in minerals with other rare earths. It is principally
   extracted from monazite (~0.007% thulium) ores found in river sands
   through ion-exchange. Newer ion-exchange and solvent extraction
   techniques have led to easier separation of the rare earths, which has
   yielded much lower costs for thulium production. The metal can be
   isolated through reduction of its oxide with lanthanum metal or by
   calcium reduction in a closed container. None of thulium's compounds
   are commercially important.

Isotopes

   Naturally occurring thulium is composed of 1 stable isotope, Tm-169
   (100% natural abundance). 31 radioisotopes have been characterized,
   with the most stable being Tm-171 with a half-life of 1.92 years,
   Tm-170 with a half-life of 128.6 days, Tm-168 with a half-life of 93.1
   days, and Tm-167 with a half-life of 9.25 days. All of the remaining
   radioactive isotopes have half-lifes that are less than 64 hours, and
   the majority of these have half lifes that are less than 2 minutes.
   This element also has 14 meta states, with the most stable being
   Tm-164m (t[½] 5.1 minutes), Tm-160m (t[½] 74.5 seconds) and Tm-155m
   (t[½] 45 seconds).

   The isotopes of thulium range in atomic weight from 145.966 u (Tm-146)
   to 176.949 u (Tm-177). The primary decay mode before the most abundant
   stable isotope, Tm-169, is electron capture, and the primary mode after
   is beta emission. The primary decay products before Tm-169 are element
   68 (erbium) isotopes, and the primary products after are element 70
   (ytterbium) isotopes.

Precautions

   Thulium has a low-to-moderate acute toxic rating and should be handled
   with care. Metallic thulium in dust form presents a fire and explosion
   hazard.

   Retrieved from " http://en.wikipedia.org/wiki/Thulium"
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   with only minor checks and changes (see www.wikipedia.org for details
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