Holmium (Ho)

Relatively soft and malleable silvery-white metallic element, which is stable in dry air at room temperature. It oxidizes in moist air and at high temperatures. It belongs to the lanthanoids. A rare-earth metal, it is found in the minerals monazite and gadolinite. It possesses unusual magnetic properties. One natural isotope, Ho-165 exists, six radioisotopes exist, the most stable being Ho-163 with a half-life of 4570 years. Holmium is used in some metal alloys, it is also said to stimulate the metabolism. Discovered by Per Theodor Cleve and J.L. Soret in Switzerland in 1879. The name homium comes from the Greek word Holmia which means Sweden. While all holmium compounds should be considered highly toxic, initial evidence seems to indicate that they do not pose much danger. The metal's dust however, is a fire hazard.
Atomic Number67
Atomic Weight164.93033
Mass Number165
Protons67 p+
Neutrons98 n0
Electrons67 e-
Holmium.jpg Animated Bohr Model Enhanced Bohr Model Bohr Model Orbital Diagram


Atomic Radius
175 pm
Atomic Volume
Covalent Radius
166 pm
Metallic Radius
Ionic Radius
90.1 pm
Crystal Radius
104.1 pm
Van der Waals radius
229.99999999999997 pm
8.8 g/cm³
Boiling Point
2,968 K
Melting Point
1,747 K
Electrons per shell2, 8, 18, 29, 8, 2
Proton Affinity
Electron Affinity
Ionization Potential
Heat of Vaporization
301 kJ/mol
Heat of Fusion
Heat of Formation
300.6 kJ/mol
Molar Heat Capacity
27.15 J/(mol K)
Specific Heat Capacity
0.165 J/(g⋅K)
Thermal Conductivity
Gas Basicity
Dipole Polarizability
156 a₀
C6 Dispersion Coefficient
Oxidation States3
Crystal StructureSimple Hexagonal (HEX)
Lattice Constant
3.58 Å
Bulk Modulus
Electrical Resistivity
Electron Configuration[Xe] 4f11 6s2
Magnetic Ordering
Magnetic Susceptibility
Poisson Ratio
Shear Modulus
Young's Modulus
Alternate Names
Adiabatic Index
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Magnetic Susceptibility
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
CategoryLanthanides, Lanthanides
CAS Group
Glawe Number23
Mendeleev Number33
Pettifor Number24
Geochemical Classrare earth & related
Goldschmidt Classlitophile
Decay Mode
Abundance in Earth's crust
1.3 mg/kg
Abundance in Oceans
0.00000022 mg/L
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universe5×10-8%

Isotopes of Holmium

Stable Isotopes
Unstable Isotopes
140Ho 141Ho 142Ho 143Ho 144Ho 145Ho 146Ho 147Ho 148Ho 149Ho 150Ho 151Ho 152Ho 153Ho 154Ho 155Ho 156Ho 157Ho 158Ho 159Ho 160Ho 161Ho 162Ho 163Ho 164Ho 166Ho 167Ho 168Ho 169Ho 170Ho 171Ho 172Ho 173Ho 174Ho 175Ho


Holmium was discovered by Swiss chemists Marc Delafontaine and Jacques-Louis Soret in 1878. They noticed the aberrant spectrographic absorption bands of the then-unknown element. Later in 1878, Per Teodor Cleve independently discovered the element while he was working on erbia earth. From the Latin word Holmia meaning Stockholm

DiscoverersJ.L. Soret
Discovery LocationSwitzerland
Discovery Year1878
Name OriginFrom Holmia, the Latinized name for Stockholm, Sweden.
Holmium is considered to be of low toxicity
Holmium has the highest magnetic strength of any naturally occurring element


Holmium is used to create the strongest artificially generated magnetic fields, when placed within high-strength magnets as a magnetic pole piece. It is one of the colorants used for cubic zirconia and glass, providing yellow or red coloring. Holmium isotopes are good neutron absorbers and are used in nuclear reactor control rods. It has very few practical applications; however, it has some unusual magnetic properties that offer some hope for future applications.


Occurs in gadolinite. Most often from monazite which is often 50% rare earth and typically 0.05% holmium.