The holmium is a metallic element belonging to the block F of the periodic table, specifically to the lanthanide period. It is therefore a member of the rare earths, together with erbium, yttrium, dysprosium and ytterbium. All these make up a series of minerals (xenotime or gadolinite) that are difficult to separate by conventional chemical methods..
Its chemical symbol is Ho, having an atomic number of 67, and being less abundant than its neighbors dysprosium (66Dy) and erbium (68Er). It is then said that it obeys the Oddo-Harkins rule. Holmium is one of those rare metals that almost no one knows or suspects of its existence; even among chemists, it is not mentioned very often.
In the fields of medicine, holmium is known for the use of its laser in surgeries to combat prostate diseases. It also represents the promising material for the manufacture of electromagnets and quantum computers, due to its unusual magnetic properties..
The trivalent compounds of holmium, Ho3+, They have the particularity of exhibiting a color dependent on the light with which they are irradiated. If it is fluorescent, the color of these compounds changes from yellow to pink. In the same way, it happens with its solutions.
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The discovery of holmium is attributed to two Swiss chemists, Marc Delafontaine and Jacques-Louis Soret, who in 1878 detected it spectroscopically while analyzing rare earth minerals in Geneva. They called it element X.
Just a year later, in 1879, the Swedish chemist Per Teodor Cleve succeeded in separating holmium oxide starting from erbia, erbium oxide (ErtwoOR3). This oxide, contaminated by other impurities, showed a brown color, which he named 'holmia', which means Stockholm in Latin..
Likewise, Cleve obtained another material of green color: 'thulia', which comes to be thulium oxide. The problem with this discovery is that none of the three chemists were able to obtain a sufficiently pure sample of holmium oxide, since it was contaminated by atoms of dysprosium, another lanthanide metal..
It was not until 1886 that the industrious French chemist, Paul Lecoq de Boisbaudran, isolated holmium oxide by fractional precipitation. This oxide later underwent chemical reactions to produce holmium salts, which were reduced in 1911 by the Swedish chemist Otto Holmberg; and thus, the first samples of metallic holmium appeared.
However, at present holmium ions, Ho3+, are extracted by ion exchange chromatography, rather than resorting to conventional reactions.
Silvery, soft, ductile and malleable metal.
67 (67Ho)
164.93 g / mol
1461 ºC
2600 ºC
At room temperature: 8.79 g / cm3
Just when it melts or melts: 8.34 g / cm3
17 kJ / mol
251 kJ / mol
27.15 J / (mol K)
1.23 on the Pauling scale
First: 581.0 kJ / mol (Ho+ gaseous)
Second: 1140 kJ / mol (Hotwo+ gaseous)
Third: 2204 kJ / mol (Ho3+ gaseous)
16.2 W / (m K)
814 nΩ m
Holmium can occur in its compounds with the following numbers or oxidation states: 0, +1 (Ho+), +2 (Hotwo+) and +3 (Ho3+). Of all of them, the +3 is by far the most common and stable. Therefore, holmium is a trivalent metal, forming compounds (ionic or partially ionic) where it participates as Ho ion3+.
For example, in the following compounds, holmium has an oxidation number of +3: HotwoOR3 (Hotwo3+OR3two-), Ho (OH)3, HoI3 (Ho3+I3-) and Hotwo(SW4)3.
The Ho3+ and its electronic transitions are responsible for the compounds of this metal to appear brown-yellow colors. However, when these are irradiated with fluorescent light, they turn pink. The same goes for your solutions.
Holmium occurs in nature as a single stable isotope: 165Ho (100% abundance). However, there are man-made radioisotopes with long half-lives. Between them we have:
-163Ho (t1/2 = 4570 years)
-164Ho (t1/2 = 29 minutes)
-166Ho (t1/2 = 26,763 hours)
-167Ho (t1/2 = 3.1 hours)
Holmium is a paramagnetic metal, but it can become ferromagnetic at a temperature of 19 K, exhibiting very strong magnetic properties. It is characterized by also having the magnetic moment (10.6 μB) largest among all chemical elements, as well as unusual magnetic permeability.
Holmium is a metal that does not rust too quickly under normal conditions, so it takes time to lose its shine. However, when heated with a lighter it turns yellowish, due to the formation of an oxide layer:
4 Ho + 3 Otwo → 2 HotwoOR3
Reacts with dilute or concentrated acids to produce their respective salts (nitrates, sulfates, etc.). However and surprisingly, it does not react with hydrofluoric acid, since a layer of HoF3 protects it from degradation.
Holmium also reacts with all halogens to produce their respective halides (HoF3, HoCl3, HoBr3 and HoI3).
Holmium crystallizes into a compact hexagonal structure, hcp (hexagonal close-packed). In theory, the Ho atoms remain cohesive thanks to the metallic bond formed by the electrons of their 4f orbitals, according to their electronic configuration:
[Xe] 4feleven 6stwo
Such interactions, as well as the energetic arrangement of its electrons, define the physical properties of holmium. No other allotrope or polymorph is known to this metal, not even under high pressure.
The holmium atom is a good neutron absorber, so it helps to control the development of nuclear reactions.
Holmium oxide solutions are used to calibrate spectrophotometers, because their absorption spectrum remains constant almost always, regardless of the impurities it contains. It also shows very characteristic sharp bands associated with the holmium atom, and not with its compounds..
Holmium atoms are capable of providing reddish coloration to glasses and artificial cubic zirconia gems.
At extremely low temperatures (30 K or less), holmium exhibits interesting magnetic properties, which are used to make powerful electromagnets, where it helps to concentrate the resulting magnetic field..
Such magnetic materials are intended for nuclear magnetic resonance; for the development of hard disks, with memories that oscillate in the order of the petabytes or terabytes; and for possibly the manufacture of quantum computers.
A yttrium-aluminum garnet (YAG) crystal can be doped with holmium atoms to emit radiation whose wavelength is 2 µm; that is, we have a holmium laser. Thanks to it, tumor tissue can be precisely cut without causing bleeding, since the energy supplied cauterizes the wounds immediately.
This laser has been used repeatedly in prostate and dental surgeries, as well as to eliminate cancer cells and kidney stones.
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