Holmium: the essentials
Holmium is relatively soft and malleable, and is stable in dry air at room temperature. It oxidises rapidly in moist air and at elevated temperatures. The metal has unusual magnetic properties. The metal is a rare earth metal found in monazite, gadolinite and other minerals.
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Holmium: historical information
Per Theodor Cleve of Sweden discovered holmium while working on erbia earth (erbium oxide). Holmium oxide (holmia) was present as an impurity in the erbia. The element is named after Cleve's native city. Pure holmia, the yellow oxide, was prepared by Homberg in 1911.
Holmium around us Read more »
Holmium has no biological role but is said to stimulate the metabolism.
Holmium is never found in nature as the free element. Holmium is found in the ores monazite sand [(Ce, La, etc.)PO4] and bastn°site [(Ce, La, etc.)(CO3)F], ores containing small amounts of all the rare earth metals. It is difficult to separate from other rare earth elements.
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Physical properties Read more »
Heat properties Read more »
- Melting point: 1734 [1461 °C (2662 °F)] K
- Boiling point: 2993 [2720 °C (4928 °F)] K
- Enthalpy of fusion: 17.0 kJ mol-1
Crystal structure Read more »
The solid state structure of holmium is: hcp (hexagonal close-packed).
Holmium: orbital properties Read more »
Holmium atoms have 67 electrons and the shell structure is 126.96.36.199.8.2. The ground state electronic configuration of neutral Holmium is [Xe].4f11.6s2 and the term symbol of Holmium is 4I15/2.
- Pauling electronegativity: 1.23 (Pauling units)
- First ionisation energy: 581.0 kJ mol‑1
- Second ionisation energy: 1140 kJ mol‑1
Isolation: holmium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure holmium is available through the reduction of HoF3 with calcium metal.
2HoF3 + 3Ca → 2Ho + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.
Holmium isotopes Read more »