Chemical element, symbol Ho and atomic number 67 / From Wikipedia, the free encyclopedia

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Holmium is a chemical element; it has symbol Ho and atomic number 67. It is a rare-earth element and the eleventh member of the lanthanide series. It is a relatively soft, silvery, fairly corrosion-resistant and malleable metal. Like many other lanthanides, holmium is too reactive to be found in native form, as pure holmium slowly forms a yellowish oxide coating when exposed to air. When isolated, holmium is relatively stable in dry air at room temperature. However, it reacts with water and corrodes readily, and also burns in air when heated.

Quick facts: Holmium, Pronunciation, Appearance, Standard ...
Holmium, 67Ho
Pronunciation/ˈhlmiəm/ (HOHL-mee-əm)
Appearancesilvery white
Standard atomic weight Ar°(Ho)
Holmium in the periodic table


Atomic number (Z)67
Groupf-block groups (no number)
Periodperiod 6
Block  f-block
Electron configuration[Xe] 4f11 6s2
Electrons per shell2, 8, 18, 29, 8, 2
Physical properties
Phase at STPsolid
Melting point1734 K (1461 °C, 2662 °F)
Boiling point2873 K (2600 °C, 4712 °F)
Density (near r.t.)8.79 g/cm3
when liquid (at m.p.)8.34 g/cm3
Heat of fusion17.0 kJ/mol
Heat of vaporization251 kJ/mol
Molar heat capacity27.15 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1432 1584 (1775) (2040) (2410) (2964)
Atomic properties
Oxidation states0,[3] +1, +2, +3 (a basic oxide)
ElectronegativityPauling scale: 1.23
Ionization energies
  • 1st: 581.0 kJ/mol
  • 2nd: 1140 kJ/mol
  • 3rd: 2204 kJ/mol
Atomic radiusempirical: 176 pm
Covalent radius192±7 pm
Color lines in a spectral range
Spectral lines of holmium
Other properties
Natural occurrenceprimordial
Crystal structure hexagonal close-packed (hcp)
Hexagonal close packed crystal structure for holmium
Thermal expansionpoly: 11.2 µm/(m⋅K) (at r.t.)
Thermal conductivity16.2 W/(m⋅K)
Electrical resistivitypoly: 814 nΩ⋅m (at r.t.)
Magnetic orderingparamagnetic
Young's modulus64.8 GPa
Shear modulus26.3 GPa
Bulk modulus40.2 GPa
Speed of sound thin rod2760 m/s (at 20 °C)
Poisson ratio0.231
Vickers hardness410–600 MPa
Brinell hardness500–1250 MPa
CAS Number7440-60-0
DiscoveryPer Theodor Cleve, Jacques-Louis Soret and Marc Delafontaine (1878)
Isotopes of holmium
Main isotopes[4] Decay
abun­dance half-life (t1/2) mode pro­duct
163Ho synth 4570 y ε 163Dy
164Ho synth 28.8 min ε 164Dy
β 164Er
165Ho 100% stable
166Ho synth 26.812 h β 166Er
166m1Ho synth 1132.6 y β 166Er
167Ho synth 3.1 h β 167Er
Symbol_category_class.svg Category: Holmium
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In nature, holmium occurs together with the other rare-earth metals (like thulium). It is a relatively rare lanthanide, making up 1.4 parts per million of the Earth's crust, an abundance similar to tungsten. Holmium was discovered through isolation by Swedish chemist Per Theodor Cleve. It was also independently discovered by Jacques-Louis Soret and Marc Delafontaine, who together observed it spectroscopically in 1878. Its oxide was first isolated from rare-earth ores by Cleve in 1878. The element's name comes from Holmia, the Latin name for the city of Stockholm.[5][6][7]

Like many other lanthanides, holmium is found in the minerals monazite and gadolinite and is usually commercially extracted from monazite using ion-exchange techniques. Its compounds in nature and in nearly all of its laboratory chemistry are trivalently oxidized, containing Ho(III) ions. Trivalent holmium ions have fluorescent properties similar to many other rare-earth ions (while yielding their own set of unique emission light lines), and thus are used in the same way as some other rare earths in certain laser and glass-colorant applications.

Holmium has the highest magnetic permeability and magnetic saturation of any element and is thus used for the pole pieces of the strongest static magnets. Because holmium strongly absorbs neutrons, it is also used as a burnable poison in nuclear reactors.

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