Science Fair Project Encyclopedia
|Name, Symbol, Number||Holmium, Ho, 67|
|Group, Period, Block||NA, 6, f|
|Density, Hardness||8800kg/m3, ND|
|Appearance|| silvery white|
|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 (weak base)|
|State of matter||solid|
|Melting point||1743 K (2678 °F)|
|Boiling point||2968 K (4883 °F)|
|Molar volume||19.01 ×10-6 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)|
|1st ionization potential||581.0 kJ/mol|
|2nd ionization potential||1140 kJ/mol|
|3rd ionization potential||2204 kJ/mol|
|4th ionization potential||4100 kJ/mol|
|Most stable isotopes|
|SI units & STP are used except where noted.|
Holmium 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.
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.
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.
Few other uses have been identified for this element.
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 .
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.
- Los Alamos National Laboratory – Holmium
- Guide to the Elements – Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
- It's Elemental – Holmium
- WebElements.com – Holmium (also used as a reference)
- EnvironmentalChemistry.com – Holmium (also used as a reference)
- American Elements – Holmium (also used as a reference)
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