|Name, Symbol, Number||Holmium, Ho, 67|
|Group, Period, Block||NA, 6 , f|
|Density, Hardness||8800kg/m3, ND|
|Atomic weight||164.9303 amu|
|Atomic radius (calc.)||247 (ND) pm|
|Covalent radius||158 pm|
|van der Waals radius||ND pm|
|e- 's per energy level||2,8,18,29,8,2|
|Oxidation states (Oxide)||3 (basique)|
|State of matter||solide|
|Melting point||1743 K (2678 °F)|
|Boiling point||2968 K (4883 °F)|
|Molar volume||19.01 ×1010-3 m3/mol|
|Heat of vaporization||241 kJ/mol|
|Heat of fusion||11.76 kJ/mol|
|Velocity of sound||2170 m/s at 293.15K|
|Electronegativity||1.23 (Pauling scale)|
|Specific heat capacity||160 J/(kg*K)|
|Electrical conductivity||1,24 106/m ohm|
|Thermal conductivity||16,2 W/(m*K)|
|1er ionization potential||581.0 kJ/mol|
|2e ionization potential||1140 kJ/mol|
|3e ionization potential||2204 kJ/mol|
|4e ionization potential||4100 kJ/mol|
|Most stable isotopes|
|SI units & STP are used except where noted.|
|Table of contents|
7 External links
A trivalent metallic rare earth element, holmium has 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 fairly corrosion-resistant and stable in dry air at standard temperature and pressure. It, however, quickly oxidizes in moist air and at higher temperatures (forming a yellowish oxide). When in pure form, holmium possesses a metallic to bright silvery luster.
Because of its magnetic properties, holmium has been used to create the strongest artificially-generated magnetic fields when it was 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;
Holmium (Holmia, Latin name for Stockholm) was discovered by Marc Delafontaine and Jacques Louis Soret in 1878 who noticed the special absorption bands of the then unknown element (they called it "Element X"). Later in 1878, Per Theodor 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.
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. It's estimated abundance in the Earth's crust is 1.3 milligrams per kilogram.
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.