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Name , symbol , atomic number Holmium, Ho, 67
Element category Lanthanoids
Group , period , block La , 6 , f
Appearance silvery white
CAS number 7440-60-0
EC number 231-169-0
ECHA InfoCard 100.028.335
Mass fraction of the earth's envelope 1.1 ppm
Atomic mass 164,93033 (2) and
Atomic radius (calculated) 175 (226) pm
Covalent radius 192 pm
Electron configuration [ Xe ] 4 f 11 6 s 2
1. Ionization energy 6th.0215 (6) eV580.99 kJ / mol
2. Ionization energy 11.781 (20) eV1 136.7 kJ / mol
3. Ionization energy 22nd.79 (3) eV2 200kJ / mol
4. Ionization energy 42.52 (8) eV4 100 kJ / mol
5. Ionization energy 63.9 (3) eV6 170 kJ / mol
Physical state firmly
Crystal structure hexagonal
density 8.78 g / cm 3 (25 ° C )
magnetism paramagnetic ( Χ m = 0.049)
Melting point 1734 K (1461 ° C)
boiling point 2873 K (2600 ° C)
Molar volume 18.74 · 10 −6 m 3 · mol −1
Heat of evaporation 251 kJ / mol
Heat of fusion 17 kJ mol −1
Speed ​​of sound 2760 m · s −1
Electric conductivity 1.23 · 10 6 A · V −1 · m −1
Thermal conductivity 16 W m −1 K −1
Oxidation states 3
Normal potential −2.33 V (Ho 3+ + 3 e - → Ho)
Electronegativity 1.23 ( Pauling scale )
isotope NH t 1/2 ZA ZE (M eV ) ZP
163 Ho {syn.} 4570 a ε 0.003 163 Dy
164 Ho {syn.} 29 min ε 0.987 164 Dy
β - 0.962 164 he
165 Ho 100  % Stable
166 Ho {syn.} 26.763 h β - 1,855 166 he
167 Ho {syn.} 3.1 h β - 1.007 167 he
For other isotopes see list of isotopes
safety instructions
GHS labeling of hazardous substances


02 - Highly / extremely flammable


H and P phrases H: 228
P: 210
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .

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


In 1878 the Swiss chemists Marc Delafontaine and Jacques-Louis Soret discovered the element spectroscopically through its deviating absorption lines. They called the new element 'X'. In 1879 the Swedish chemist Per Teodor Cleve discovered the new element independently of the two Swiss people and isolated it as a yellow oxide from impure erbium (erbium oxide). Cleve used a method developed by Carl Gustav Mosander ; it first separated off any known impurities before attempting to separate the rest. He received a brown residue, which he named Holmia, and a green residue, which was named Thulia .

It was not until 1911 that the Swedish chemist Holmberg succeeded in obtaining pure holmium oxide. It is not known whether he adopted the name Holmium, suggested by Cleve for the Swedish capital Stockholm , or regarded it as a derivative of his own name.

Metallic pure holmium was first produced in 1940.


In natural occurrences, holmium occurs only in compounds. Well-known minerals containing holmium are:

Extraction and presentation

After an elaborate separation of the other holmium companions, the oxide is converted with hydrogen fluoride to holmium fluoride . It is then reduced to the metallic holmium with calcium to form calcium fluoride . The remaining calcium residues and impurities are separated in an additional remelting process in a vacuum .



The silver-white shiny metal of the rare earths is soft and malleable.

Holmium has special magnetic properties. It is far superior to iron in its ferromagnetic properties . Holmium has, together with dysprosium the highest magnetic moment (10.6 μ B ) of all chemical elements naturally occurring. It forms magnetic bonds with yttrium .

Holmium is relatively stable in dry air ; in humid or warm air it tarnishes quickly with the formation of a yellowish oxide layer. At temperatures above 150 ° C it burns to the sesquioxide Ho 2 O 3 . With water it reacts with evolution of hydrogen to hydroxide . It dissolves in mineral acids with the formation of hydrogen.

In its compounds it has an oxidation number of +3, the Ho 3+ cations form yellow solutions in water. Under special reductive conditions, the oxidation number +2 can also be achieved with the chlorides, e.g. B. in holmium (II, III) chloride Ho 5 Cl 11 , but the pure holmium (II) chloride does not exist.


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

Other uses:


Holmium has no known biological function.

safety instructions

Holmium and holmium compounds are considered to be of low toxicity. Metal dusts are flammable and explosive.


Web links

Commons : Holmium  - collection of images, videos and audio files
Wiktionary: Holmium  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ Harry H. Binder: Lexicon of the chemical elements. S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
  2. The values ​​for the properties (info box) are taken from www.webelements.com (Holmium) , unless otherwise stated .
  3. ^ IUPAC, Standard Atomic Weights Revised v2 ( Memento of March 3, 2016 in the Internet Archive ).
  4. CIAAW, Standard Atomic Weights Revised 2013 .
  5. a b c d e entry on holmium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 13, 2020.
  6. a b c d e entry on holmium at WebElements, https://www.webelements.com , accessed on June 13, 2020.
  7. ^ NN Greenwood, A. Earnshaw: Chemistry of the elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 1579.
  8. Robert C. Weast (Ed.): CRC Handbook of Chemistry and Physics . CRC (Chemical Rubber Publishing Company), Boca Raton 1990, ISBN 0-8493-0470-9 , pp. E-129 to E-145. Values ​​there are based on g / mol and given in cgs units. The value specified here is the SI value calculated from it, without a unit of measure.
  9. a b Yiming Zhang, Julian RG Evans, Shoufeng Yang: Corrected Values ​​for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks. In: Journal of Chemical & Engineering Data . 56, 2011, pp. 328-337, doi: 10.1021 / je1011086 .
  10. a b Entry on holmium, powder in the GESTIS substance database of the IFA , accessed on April 26, 2017(JavaScript required) .
  11. Dysprosium. www.americanelements.com, accessed on March 27, 2016 (English).
  12. Holmium. www.americanelements.com, accessed on March 27, 2016 (English).
  13. The use of medium-power holmium lasers in endourology ( Memento from March 4, 2016 in the Internet Archive ) (PDF; 46 kB).
  14. starna.de: Holmium glass - UV and visible wavelength .