Holmium, I, Atomic number 67

General

Holmium is a chemical element with the element symbol Ho and atomic number 67. In the periodic table it is in the group of lanthanides and is thus also one of the rare earth metals.

1878 discovered the Swiss chemist Marc Delafontaine and Jacques-Louis Soret element spectroscopically by its deviating absorption lines. The new element they called> X <. 1879 discovered by the Swedish chemist Per Teodor Cleve independently of the new element of the two Swiss and isolated it as a yellow oxide of erbium impure (Erbium). Cleveland used a method developed by Carl Gustav Mosander; He initially gave all known impurities, before trying, to separate the rest. He received a brown residue, which he called Holmia, and the green residue, who was named Thulia. Only 1911 Holmberg managed the Swedish chemist, the production of pure holmium. Whether he got the name holmium, proposed by Cleveland for the Swedish capital Stockholm, adopted or considered as a derivative of his own name, is not known.

Pure holmium metal was first 1940 produced. Holmium occurs naturally only in compounds. Minerals are known holmiumhaltige:

Gadolinit (Deposits are depleted in Ytterby)
Monazite (This,The,Th,Nd,And)PO4

Extraction

After an extensive separation of the other Holmiumbegleiter, the oxide with hydrogen fluoride to Holmiumfluorid reacted. Is then reduced with calcium to form calcium fluoride to the metallic holmium. Separation of remaining calcium residues and impurities occur in an additional remelting in vacuo.

Special features

The silver-white lustrous metal of the rare earth is soft and malleable.

Holmium has special magnetic properties. In its ferromagnetic properties, it is far superior to the iron. With 10,6 μB it has the highest magnetic moment of a naturally occurring chemical element. With yttrium, it forms magnetic compounds.

In dry air is relatively resistant to Holmium, in moist or warm air, it runs quickly, forming a yellowish oxide. At temperatures above 150 ° C, it burns Ho2O3 the sesquioxide. With water it reacts with evolution of hydrogen to hydroxide. In mineral acids it dissolves with the formation of hydrogen on.

In its compounds it is the oxidation number +3 before, the Ho3 ions form yellow solutions in water. Under special conditions for the reductive chlorides can also be an oxidation number +2 be realized, e.g.. the holmium(II,III)chlorid Ho5Cl11, However, there is the pure holmium(II)chloride does not.

Use

Because of its excellent magnetic properties of holmium pole pieces are used for high-performance magnets to produce the strongest magnetic fields.

Applications:

  1. A magnetic bubble memory using thin film alloys of holmium iron, Holmium-nickel-cobalt and holmium.
  2. Control rods in breeder reactors.
  3. Doping of yttrium iron garnet (YIG), Yttrium-aluminum-shell (YAG) und Yttrium-Lithium-Fluorid (YLF) for solid-state laser (Holmium laser having an emission wavelength of 2.1 microns [7]) and microwave components in medical.
  4. Holmium oxide to produce a yellow glass u.a. because of its sharp absorption bands for calibration of photometers.

Holmium has no known biological function.

Holmium and Holmiumverbindungen are regarded as less toxic. Metal dusts are fire- and potentially dangerous.

General
Name, Symbol, Number Holmium, I, 67
Series Lanthanides
group, Period, Block The, 6, f
Appearance silvery white
CAS-Nummer 7440-60-0
Mass fraction of element 1,1 ppm
Atomic
Atomic mass 164,93032 you
Atomradius 175 pm
Kovalenter Radius 192 pm
Elektronenkonf. [Car] 4f(11) 6s2
1. Ionization 581,0 KJ / mol
2. Ionization 1170 KJ / mol
3. Ionization 2204 KJ / mol
Physically
Physical State fixed
Crystal structure hexagonal
Density 8,78 g/cm3 (25 ° C)
Magnetism paramagnetisch (χm = 0,049)
Melting point 1734 K (1431 C)
Boiling point 2993 K (2720 C)
Molar Volume 18,74 * 10(-6)m(3)/mol
Heat of vaporization 265 KJ / mol
Schmelzwärme 17,0 KJ / mol
Electrical conductivity 1,23*10(6) A/(V * m)
Thermal conductivity 16 W /(m*K)
This entry was posted in Rare earth and tagged , , , , , , , , , , , . Bookmark the permalink.

Leave a Reply