   #copyright

Terbium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                65            gadolinium ← terbium → dysprosium
                 -
                ↑
                Tb
                ↓
                Bk

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                      Name, Symbol, Number terbium, Tb, 65
                                               Chemical series lanthanides
                                            Group, Period, Block n/a, 6, f
                                                  Appearance silvery white
                                           Atomic mass 158.92535 (2) g/mol
                                     Electron configuration [Xe] 4f^9 6s^2
                                    Electrons per shell 2, 8, 18, 27, 8, 2
                                                       Physical properties
                                                               Phase solid
                                       Density (near r.t.) 8.23 g·cm^−3
                                    Liquid density at m.p. 7.65 g·cm^−3
                                                     Melting point 1629  K
                                                    (1356 ° C, 2473 ° F)
                                                      Boiling point 3503 K
                                                    (3230 ° C, 5846 ° F)
                                         Heat of fusion 10.15 kJ·mol^−1
                                     Heat of vaporization 293 kJ·mol^−1
                          Heat capacity (25 °C) 28.91 J·mol^−1·K^−1

   CAPTION: Vapor pressure

                               P/Pa   1    10   100    1 k    10 k  100 k
                              at T/K 1789 1979 (2201) (2505) (2913) (3491)

                                                         Atomic properties
                                               Crystal structure hexagonal
                                                     Oxidation states 3, 4
                                                      (weakly basic oxide)
                                  Electronegativity  ? 1.2 (Pauling scale)
                                                       Ionization energies
                                           ( more) 1st: 565.8 kJ·mol^−1
                                                    2nd: 1110 kJ·mol^−1
                                                    3rd: 2114 kJ·mol^−1
                                                      Atomic radius 175 pm
                                              Atomic radius (calc.) 225 pm
                                                             Miscellaneous
                                           Magnetic ordering ferromagnetic
                                                                in dry ice
                                 Electrical resistivity ( r.t.) (α, poly)
                                                             1.150 µΩ·m
                       Thermal conductivity (300 K) 11.1 W·m^−1·K^−1
                                      Thermal expansion ( r.t.) (α, poly)
                                                           10.3 µm/(m·K)
                               Speed of sound (thin rod) (20 °C) 2620 m/s
                                        Young's modulus (α form) 55.7 GPa
                                          Shear modulus (α form) 22.1 GPa
                                           Bulk modulus (α form) 38.7 GPa
                                             Poisson ratio (α form) 0.261
                                                  Vickers hardness 863 MPa
                                                  Brinell hardness 677 MPa
                                             CAS registry number 7440-27-9
                                                         Selected isotopes

                 CAPTION: Main article: Isotopes of terbium

                                 iso    NA  half-life DM  DE ( MeV)   DP
                                ^157Tb syn  71 y      ε   0.060     ^157Gd
                                ^158Tb syn  180 y     ε   1.220     ^158Gd
                                                      β^- 0.937     ^158Dy
                                ^159Tb 100% Tb is stable with 94 neutrons

                                                                References

   Terbium ( IPA: /ˈtɛː(r)biəm/) is a chemical element in the periodic
   table that has the symbol Tb and atomic number 65.

Notable characteristics

   Terbium is a silvery-white rare earth metal that is malleable, ductile
   and soft enough to be cut with a knife. It is reasonably stable in air,
   and two crystal allotropes exist, with a transformation temperature of
   1289 °C.

Applications

   Terbium is used to dope calcium fluoride, calcium tungstate and
   strontium molybdate, materials that are used in solid-state devices,
   and as a crystal stabilizer of fuel cells which operate at elevated
   temperatures, together with ZrO[2]. Terbium is also used in alloys and
   in the production of electronic devices, its oxide is used in green
   phosphors in fluorescent lamps and colour TV tubes. Sodium terbium
   borate is used in solid state devices.

History

   Terbium was discovered in 1843 by Swedish chemist Carl Gustaf Mosander,
   who detected it as an impurity in Yttrium-oxide, Y[2]O[3], and named
   after the village Ytterby in Sweden. It was not isolated in pure form
   until the recent advent of ion exchange techniques.

   Terbium is classified as a rare earth element. The term "rare" is
   misleading because terbium is more common than metals such as silver
   and mercury. The name "rare earth" meant something else to early
   chemists. It was used because the rare earth elements were very
   difficult to separate from each other. They were not "rare" in the
   Earth, but they were "rarely" used for anything.

Occurrence

   Terbium is never found in nature as the free element, but it is
   contained in many minerals, including cerite, gadolinite, monazite
   ((Ce,LaTh,Nd,Y)PO[4], which contains up to 0.03% of terbium), xenotime
   (YPO[4]) and euxenite ((Y,Ca,Er,La,Ce,U,Th)(Nb,Ta,Ti)[2]O[6], which
   contains 1% or more of terbium).

Compounds

   Terbium compounds include:
     * Fluorides
          + TbF[3]
          + TbF[4]
     * Chlorides
          + TbCl[3]
     * Bromides
          + TbBr[3]
     * Iodides
          + TbI[3]
     * Oxides
          + Tb[2]O[3]
          + Tb[4]O[7]
     * Sulfides
          + Tb[2]S[3]
     * Nitrides
          + TbN

Isotopes

   Naturally occurring terbium is composed of 1 stable isotope, 159-Tb. 33
   radioisotopes have been characterized, with the most stable being
   158-Tb with a half-life of 180 years, 157-Tb with a half-life of 71
   years, and 160-Tb with a half-life of 72.3 days. All of the remaining
   radioactive isotopes have half-lifes that are less than 6.907 days, and
   the majority of these have half lifes that are less than 24 seconds.
   This element also has 18 meta states, with the most stable being
   156m1-Tb (t[½] 24.4 hours), 154m2-Tb (t[½] 22.7 hours) and 154m1-Tb
   (t[½] 9.4 hours).

   The primary decay mode before the most abundant stable isotope, 159-Tb,
   is electron capture, and the primary mode after is beta minus decay.
   The primary decay products before 159-Tb are element Gd (gadolinium)
   isotopes, and the primary products after are element Dy (dysprosium)
   isotopes.

Precautions

   As with the other lanthanides, terbium compounds are of low to moderate
   toxicity, although their toxicity has not been investigated in detail.
   Terbium has no known biological role.
   Retrieved from " http://en.wikipedia.org/wiki/Terbium"
   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.
