What is Holmium
Holmium (pronunciation: HOHL-mee-em) is a silvery metal belonging to the group of lanthanides and represented by the chemical symbol Ho [1, 2]. It has one stable naturally occurring isotope, 165Ho, with a natural abundance of 100% while its most stable radioisotope, 163Ho has a half-life period of 4,570 years .
Where is Holmium Found
Although Holmium does not freely occur in nature, it is found as a component in several minerals including bastnaesite and monazite [1, 4]. Commercially, it is obtained from monazite, bastnaesite, and xenotime ores through ion exchange and is isolated by calcium reduction of its anhydrous fluoride [1, 4, 5]. While top 3 holmium producing countries include China, Russia, and Malaysia, the top 3 nations with the largest holmium holdings in the world are China, the CIS countries, and the USA .
Origin of its Name: It is derived from ‘Holmia’, the Latin name for the Swedish capital Stockholm .
Who discovered it: Holmium was discovered by the Swedish chemist Per Teodor Cleve, and independently by the Swiss chemist Louis Soret along with Marc Delafontaine .
When and How was it Discovered
In 1878, Louis Soret and Marc Delafontaine while investigating yttrium at Geneva found that it was contaminated with other lanthanoids, observing unexplained spectral lines [1, 4]. They extracted a new element ‘X’, which is now known as holmium . In that same year, Per Teodor Cleve worked with erbium at Uppsala to discover a brown and a green substance, which he named holmia (holmium oxide) and thulia (thulium oxide) respectively .
The pure form of holmium was separated by the Swedish botanist Otto Holmberg .
|Atomic number||67 |
|CAS number||7440-60-0 |
|Position in the periodic table||Group||Period||Block|
|Lanthanides ||6 ||f |
Properties and Characteristics of Holmium
|Atomic mass||164.930 amu |
|Relative atomic mass||164.930 |
|Color||Bright silvery-white [1, 4]|
|Melting point/freezing point||1472 °C, 2682 °F |
|Boiling point||2700 °C, 4892 °F |
|Density||8.80 g cm-3 |
|State of matter at room temperature (solid/liquid/gas)||Solid [1, 4]|
|– Brinell||746 MPa |
|– Mohs||1.65 |
|– Vickers||481 MPa |
|Electrical conductivity||1.1X106 S/m |
|Thermal (heat) conductivity||16 W/(m K) |
|Specific heat||165 J kg-1 K-1 |
|Bulk modulus||40.2 GPa |
|Shear modulus||26.3 GPa |
|Young’s modulus||64.8 GPa |
|– Temperature (K)||400||600||800||1000||1200||1400||1600||1800||2000||2200||2400|
|– Pressure (Pa)||–||–||3.20 X 10-9||2.32 X 10-5||8.37 X 10-3||0.546||12.3||–||–||–||–|
|Oxidation state/Oxidation number||(+2) +3 |
|Isotopes||Isotope||Mass||Abundance (%)||Half-life||Mode of decay|
Atomic Data of Holmium (Element 67)
|Valence electrons||2 |
|– n||4 |
|– ℓ||3 |
|– mℓ||0 |
|– ms||-1/2 |
|Electron configuration (noble gas configuration)||[Xe] 4f116s2 |
|– Number of electrons||67 |
|– Number of neutrons||98 |
|– Number of protons||67 |
|Radius of Atom|
|– Atomic radius||2.30 Å |
|– Covalent radius||1.79 Å |
|Electronegativity (Pauling-scale)||1.23 |
|Electron affinity||Unknown |
|Ionization energy (kJ mol-1)||1st||2nd||3rd||4th||5th||6th||7th||8th|
How is Holmium Used
- Since it is an excellent absorber of neutrons, its isotopes are used in the control rods of nuclear reactors to control fission chain reactions [1, 4].
- Holmium has special magnetic properties, and so its alloys are used for producing magnets and flux concentrators for high-intensity magnetic fields .
- Holmium-doped solid-state lasers are used for medical procedures including breaking-up of kidney stones (lithotripsy), and benign prostatic hyperplasia surgeries like prostate enucleation (HoLEP), resection (HoLRP), and ablation (HoLAP) [4, 8].
- Holmium oxide or holmia can be used as a red or yellow coloring agent for cubic zirconia and glass .
The element 67 is not considered to be harmful because it has low toxicity . However, holmium salts can be toxic if orally consumed, inhaled, or injected in large amounts .
- Holmium is graphically represented by an image of the coat of arms of Stockholm, the Swedish capital after which the element is named .
- The element quickly oxidizes at high temperatures and in the moist air .
Cost of Holmium
The cost of pure holmium is $8.6 per gram and $8600 per kg , but in bulk, its price is $10 per gram .