Home Element Metal Holmium


What is Holmium?

Holmium is a chemical element or rare earth metal in the periodic table with the symbol Ho and atomic number 67. Like other lanthanides, it is the reactive and softest metal that can form a yellowish oxide coating when exposed to air or oxygen.

Holmium element or rare earth metal symbol Ho, uses, properties, and facts

Holmium is used in solid-state lasers for microwave equipment and optical fibers technology. It is also used to create a magnetic flux concentrator for making artificial magnets and glasses which are used in optical spectrophotometers for calibration.

It was discovered in 1878 by Swedish chemist Per Theodor Cleve and independently by Jacques-Louis Soret and Marc Delafontaine. The name of the element comes from the Latin word Holmia means the city of Stockholm.

Where is Holmium Found?

Holmium is found in nature together with other rare-earth metals. The abundance of the metal is similar to that of tungsten. Like many other lanthanides, it is found in the minerals monazite and gadolinite and extracted or separated commercially by ion-exchange chromatography techniques.

Most of the world’s production of holmium comes from the mining areas of China, the USA, Brazil, India, Sri Lanka, and Australia.


Naturally occurring holmium has one stable isotope with an atomic mass of 165. It also contains 35 synthetic radioactive isotopes that can be synthesized by various artificial nuclear reactions. Most of these radioactive isotopes have half-lives of less than 3 hours.

The metastable 166m1Ho (half-life of around 1200 years) has been used in nuclear physics for the calibration of gamma-ray spectrometers.


Holmium is a soft, malleable, lustrous metal with high electrical conductance. It is a silvery colour metal belonging to the lanthanide series of the periodic table.

Symbol Ho
Discovery Per Teodor Cleve and independently by Marc Delafontaine and Louis Soret in 1878
Name derived from The Latin name for Stockholm means Holmia
Common isotope 67Ho165
Oxidation state +3
CAS number 7440-60-0
Periodic properties
Atomic number 67
Relative atomic mass 164.930
Electron per cell 2, 8, 18, 29, 8, 2
Electronic configuration [Xe] 4f11 6s2
Block f-block
Group Lanthanides
Period 6
Physical properties
State at 20 °C Solid
Melting point 1472 °C, 1745 K
Boiling point 2700 °C, 2973 K
Molar heat capacity 27.15 J mol−1 K1
Crystal structure ​​hexagonal close-packed (hcp)
Density 8.80 g/cm3
Heat of fusion 17 kJ mol−1
Heat of vaporization 251 kJ mol−1
Atomic properties
Atomic radius (non-bonded) 2.30 Å
Covalent radius 1.79 Å
Electronegativity 1.23 (Pauling scale)
Electron affinity Unknown
Ionization energy (kJ/mol) 1st 2nd 3rd
580.99 1138.50 2203.73

Holmium Electron Configuration

The 67 electrons of holmium are distributed in different energy levels or orbitals to give the following electronic configuration,

Holmium (Ho) atomic structure and electron per shell with atomic number, atomic mass, electronic configuration and energy levels

Holmium in the Periodic Table

The rare earth metal holmium is placed in the f-block of the periodic table. It is lanthanide that lies between dysprosium and erbium.

Holmium element (lanthanide or rare earth metal) symbol Ho and position in the periodic table with atomic number, electronic configuration

Chemical Properties

Holmium is a highly reactive and electropositive rare earth metal that is stable in dry air at ordinary temperatures but rapidly dull in humid atmospheres. It burns in the air to form yellow oxide Ho2O3.
4 Ho + 3 O2 → 2 Ho2O3

It stands far above hydrogen in the electrochemical series. Therefore, it reacts slowly with cold water and rapidly with hot water to liberate hydrogen gas.
2 Ho + 6 H2O → 2 Ho(OH)3 + 3 H2

Reactions with acids are more vigorous but the metal does not dissolve in alkalies. It dissolves readily in dilute sulfuric acid to form solutions containing the yellow holmium (III) ions.
2 Ho + 3 H2SO4 → 2 Ho3+ + 3 SO4−2 + 3 H2

Holmium is normally from trihalides with halogens like fluorine, chlorine, bromine, and iodine.
2 Ho + 3 X2 (X = F, Cl, Br, I) → 2 HoX3

Facts About Holmium

  • It is not found in nature in free elements due to its high reactivity.
  • It is one of the rare lanthanides that is 20 times more abundant than silver.
  • It is the sixth most volatile lanthanide after ytterbium, europium, samarium, thulium and dysprosium.
  • Like many lanthanides, it forms chemical compounds in the +3 oxidation number or state but in the +2 state, it forms fluoride (HoF3) and chloride (HoCl3) compounds.
  • It combined with yttrium to form a highly magnetic compound.
  • It does not play any biological role in human beings but holmium salts can simulate the metabolism of human beings.

What is Holmium Used for?

  • Holmium is alloyed with other metals to make the strongest artificial magnets.
  • It is used to control chain reactions in nuclear power reactors because it has high neutron absorption properties.
  • Holmium-doped yttrium iron garnet (YIG) and yttrium lithium fluoride (YLF) have been used for making solid-state lasers. These lasers are used widely in microwave and optical fiber technology.
  • The glass containing holmium oxide has sharp optical absorption peaks with a wavelength range of 200–900 nm. Therefore, it can be employed in optical spectrophotometers for the purpose of calibration.
  • The long-lived metastable radioactive isotope of holmium (166m1Ho) is used for the calibration of gamma-ray spectrometers.