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Holmium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                67              dysprosium ← holmium → erbium
                 -
                ↑
                Ho
                ↓
                Es

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                      Name, Symbol, Number holmium, Ho, 67
                                               Chemical series lanthanides
                                            Group, Period, Block n/a, 6, f
                                                  Appearance silvery white
                                           Atomic mass 164.93032 (2) g/mol
                                    Electron configuration [Xe] 4f^11 6s^2
                                    Electrons per shell 2, 8, 18, 29, 8, 2
                                                       Physical properties
                                                               Phase solid
                                       Density (near r.t.) 8.79 g·cm^−3
                                    Liquid density at m.p. 8.34 g·cm^−3
                                                     Melting point 1734  K
                                                    (1461 ° C, 2662 ° F)
                                                      Boiling point 2993 K
                                                    (2720 ° C, 4928 ° F)
                                          Heat of fusion 17.0 kJ·mol^−1
                                     Heat of vaporization 265 kJ·mol^−1
                          Heat capacity (25 °C) 27.15 J·mol^−1·K^−1

   CAPTION: Vapor pressure

                               P/Pa   1    10   100    1 k    10 k  100 k
                              at T/K 1432 1584 (1775) (2040) (2410) (2964)

                                                         Atomic properties
                                               Crystal structure hexagonal
                                                        Oxidation states 3
                                                            ( basic oxide)
                                    Electronegativity 1.23 (Pauling scale)
                                                       Ionization energies
                                           ( more) 1st: 581.0 kJ·mol^−1
                                                    2nd: 1140 kJ·mol^−1
                                                    3rd: 2204 kJ·mol^−1
                                                      Atomic radius 175 pm
                                                             Miscellaneous
                                                 Magnetic ordering no data
                          Electrical resistivity ( r.t.) (poly) 814 nΩ·m
                       Thermal conductivity (300 K) 16.2 W·m^−1·K^−1
                                          Thermal expansion ( r.t.) (poly)
                                                           11.2 µm/(m·K)
                               Speed of sound (thin rod) (20 °C) 2760 m/s
                                                  Young's modulus 64.8 GPa
                                                    Shear modulus 26.3 GPa
                                                     Bulk modulus 40.2 GPa
                                                       Poisson ratio 0.231
                                                  Vickers hardness 481 MPa
                                                  Brinell hardness 746 MPa
                                             CAS registry number 7440-60-0
                                                         Selected isotopes

                 CAPTION: Main article: Isotopes of holmium

                                 iso    NA  half-life DM  DE ( MeV)   DP
                                ^163Ho syn  4570 a    ε   0.003     ^163Dy
                                ^164Ho syn  29 min    ε   0.987     ^164Dy
                                ^165Ho 100% Ho is stable with 98 neutrons
                                ^166Ho syn  26,763 h  β^- 1.855     ^166Er
                                ^167Ho syn  3,1 h     β^- 1.007     ^167Er

                                                                References

   Holmium ( IPA: /ˈhəʊlmiəm/) is a chemical element in the periodic table
   that has the symbol Ho and atomic number 67. Part of the lanthanide
   series, holmium is a relatively soft and malleable silvery-white
   metallic element, which is stable in dry air at room temperature. A
   rare earth metal, it is found in the minerals monazite and gadolinite.

Notable characteristics

   A trivalent metallic rare earth element, holmium has the highest
   magnetic moment (10.6µB) of any naturally-occurring element and
   possesses other unusual magnetic properties. When combined with
   yttrium, it forms highly magnetic compounds.

   Holmium is a relatively soft and malleable element that is fairly
   corrosion-resistant and stable in dry air at standard temperature and
   pressure. In moist air and at higher temperatures, however, it quickly
   oxidizes, forming a yellowish oxide. In pure form, holmium possesses a
   metallic, bright silvery luster.

Applications

   Because of its magnetic properties, holmium has been used to create the
   strongest artificially-generated magnetic fields when placed within
   high-strength magnets as a magnetic pole piece (also called a magnetic
   flux concentrator). Since it can absorb nuclear fission-bred neutrons,
   the element is also used in nuclear control rods. Other commercial
   applications of the element include;
     * its very high magnetic moment is suitable for use in yttrium-iron-
       garnet (YIG) and yttrium-lanthanum- fluoride (YLF) solid state
       lasers found in microwave equipment (which are in turn found in a
       variety of medical and dental settings).

     * Holmium oxide is used as a yellow glass coloring.
     * Holmium is used in a laser to break up kidney stones while being
       minimally invasive

   Few other uses have been identified for this element.

History

   Holmium (Holmia, Latin name for Stockholm) was discovered by Marc
   Delafontaine and Jacques Louis Soret in 1878 who noticed the aberrant
   spectrographic absorption bands of the then-unknown element (they
   called it "Element X"). Later in 1878, Per Teodor Cleve independently
   discovered the element while he was working on erbia earth ( erbium
   oxide).

   Using the method developed by Carl Gustaf Mosander, Cleve first removed
   all of the known contaminants from erbia. The result of that effort was
   two new materials, one brown and one green. He named the brown
   substance holmia (after the Latin name for Cleve's home town,
   Stockholm) and the green one thulia. Holmia was later found to be the
   holmium oxide and thulia was thulium oxide.

Occurrence

   Like all other rare earths, holmium is not naturally found as a free
   element. It does occur combined with other elements in the minerals
   gadolinite, monazite, and in other rare-earth minerals. It is
   commercially extracted via ion-exchange from monazite sand (0.05%
   holmium) but is still difficult to separate from other rare earths. The
   element has been isolated through the reduction of its anhydrous
   chloride or fluoride with metallic calcium. Its estimated abundance in
   the Earth's crust is 1.3 milligrams per kilogram.

Isotopes

   Natural holmium contains one stable isotope, holmium 165. Some
   synthetic radioactive isotopes are known, the most stable one is
   holmium 163, with a half life of 4570 years. All other radioisotopes
   have half lives not greater than 1.117 days, and most have half lives
   under 3 hours.

Precautions

   The element, as with other rare earths, appears to have a low acute
   toxic rating. Holmium plays no biological role in humans but may be
   able to stimulate metabolism.

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