   #copyright

Praseodymium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                59            cerium ← praseodymium → neodymium
                 -
                ↑
                Pr
                ↓
                Pa

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                 Name, Symbol, Number praseodymium, Pr, 59
                                               Chemical series lanthanides
                                            Group, Period, Block n/a, 6, f
                                                  Appearance grayish white
                                           Atomic mass 140.90765 (2) g/mol
                                     Electron configuration [Xe] 4f^3 6s^2
                                    Electrons per shell 2, 8, 18, 21, 8, 2
                                                       Physical properties
                                                               Phase solid
                                       Density (near r.t.) 6.77 g·cm^−3
                                    Liquid density at m.p. 6.50 g·cm^−3
                                                     Melting point 1208  K
                                                     (935 ° C, 1715 ° F)
                                                      Boiling point 3793 K
                                                    (3520 ° C, 6368 ° F)
                                          Heat of fusion 6.89 kJ·mol^−1
                                     Heat of vaporization 331 kJ·mol^−1
                          Heat capacity (25 °C) 27.20 J·mol^−1·K^−1

   CAPTION: Vapor pressure

                               P/Pa   1    10   100    1 k    10 k  100 k
                              at T/K 1771 1973 (2227) (2571) (3054) (3779)

                                                         Atomic properties
                                               Crystal structure hexagonal
                                                        Oxidation states 3
                                                      (mildly basic oxide)
                                    Electronegativity 1.13 (Pauling scale)
                                                       Ionization energies
                                             ( more) 1st: 527 kJ·mol^−1
                                                    2nd: 1020 kJ·mol^−1
                                                    3rd: 2086 kJ·mol^−1
                                                      Atomic radius 185 pm
                                              Atomic radius (calc.) 247 pm
                                                             Miscellaneous
                                                 Magnetic ordering no data
                                 Electrical resistivity ( r.t.) (α, poly)
                                                             0.700 µΩ·m
                       Thermal conductivity (300 K) 12.5 W·m^−1·K^−1
                                      Thermal expansion ( r.t.) (α, poly)
                                                            6.7 µm/(m·K)
                               Speed of sound (thin rod) (20 °C) 2280 m/s
                                        Young's modulus (α form) 37.3 GPa
                                          Shear modulus (α form) 14.8 GPa
                                           Bulk modulus (α form) 28.8 GPa
                                             Poisson ratio (α form) 0.281
                                                  Vickers hardness 400 MPa
                                                  Brinell hardness 481 MPa
                                             CAS registry number 7440-10-0
                                                         Selected isotopes

               CAPTION: Main article: Isotopes of praseodymium

                                 iso    NA  half-life DM  DE ( MeV)   DP
                                ^141Pr 100% Pr is stable with 82 neutrons
                                ^142Pr syn  19.12 h   β^- 2.162     ^142Nd
                                                      ε   0.745     ^142Ce
                                ^143Pr syn  13.57 d   β^- 0.934     ^143Nd

                                                                References

   Praseodymium ( IPA: /ˌpreɪziə(ʊ)ˈdɪmiəm, ˌpreɪsi-/) is a chemical
   element in the periodic table that has the symbol Pr and atomic number
   59.

Notable characteristics

   Praseodymium is a soft silvery metallic element, and belongs to the
   lanthanide group. It is somewhat more resistant to corrosion in air
   than europium, lanthanum, cerium, or neodymium, but it does develop a
   green oxide coating that spalls off when exposed to air, exposing more
   metal to oxidation. For this reason, praseodymium should be stored
   under a light mineral oil or sealed in glass.

Applications

   Uses of praseodymium:
     * As an alloying agent with magnesium to create high-strength metals
       that are used in aircraft engines.
     * Praseodymium forms the core of carbon arc lights which are used in
       the motion picture industry for studio lighting and projector
       lights.
     * Praseodymium compounds are used to give glasses and enamels a
       yellow colour.
     * Praseodymium is a component of didymium glass, which is used to
       make certain types of welder's and glass blower's goggles.
     * Dr. Matthew Sellars of the Laser Physics Centre at the Australian
       National University in Canberra, Australia slowed down a light
       pulse to a few hundred meters per second using praseodymium mixed
       with silicate crystal.

History

   The name praseodymium comes from the Greek prasios, meaning green, and
   didymos, or twin. Praseodymium is frequently misspelled as
   Praseodynium.

   In 1841, Mosander extracted the rare earth didymium from lanthana. In
   1874, Per Teodor Cleve concluded that didymium was in fact two
   elements, and in 1879, Lecoq de Boisbaudran isolated a new earth,
   samarium, from didymium obtained from the mineral samarskite. In 1885,
   the Austrian chemist baron Carl Auer von Welsbach separated didymium
   into two elements, praseodymium and neodymium, which gave salts of
   different colors.

Occurrence

   Praseodymium is available in small quantities in Earth’s crust
   (9,5ppm). It is found in the rare earth minerals monazite and
   bastnasite, and can be recovered from bastnasite or monazite by an ion
   exchange process.

   Praseodymium also makes up about 5% of Misch metal.

Compounds

   Praseodymium compounds include:
     * Fluorides
          + PrF[2]
          + PrF[3]
          + PrF[4]
     * Chlorides
          + PrCl[3]
     * Bromides
          + PrBr[3]
          + Pr[2]Br[5]
     * Iodides
          + PrI[2]
          + PrI[3]
          + Pr[2]I[5]
     * Oxides
          + PrO[2]
          + Pr[2]O[3]
     * Sulfides
          + PrS
          + Pr[2]S[3]
     * Selenides
          + PrSe
     * Tellurides
          + PrTe
          + Pr[2]Te[3]
     * Nitrides
          + PrN

Isotopes

   Naturally occurring praseodymium is composed of one stable isotope,
   ^141Pr. 38 radioisotopes have been characterized with the most stable
   being ^143Pr with a half-life of 13.57 days and ^142Pr with a half-life
   of 19.12 hours. All of the remaining radioactive isotopes have
   half-lifes that are less than 5.985 hours and the majority of these
   have half lifes that are less than 33 seconds. This element also has 6
   meta states with the most stable being ^138mPr (t[½] 2.12 hours),
   ^142mPr (t[½] 14.6 minutes) and ^134mPr (t[½] 11 minutes).

   The isotopes of praseodymium range in atomic weight from 120.955 u
   (^121Pr) to 158.955 u (^159Pr). The primary decay mode before the
   stable isotope, ^141Pr, is electron capture and the primary mode after
   is beta minus decay. The primary decay products before ^141Pr are
   element 58 (Cerium) isotopes and the primary products after are element
   60 (Neodymium) isotopes.

Precautions

   Like all rare earths, praseodymium is of low to moderate toxicity.
   Praseodymium has no known biological role.
   Retrieved from " http://en.wikipedia.org/wiki/Praseodymium"
   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.
