Holmium (Ho)

Holmium (symbol Ho) is the chemical element with atomic number 67: a lanthanide (rare earth), solid at 0 °C, with an atomic mass of 164.93 u. Discovered in 1878 (Marc Delafontaine, Jacques-Louis Soret and Per Teodor Cleve).

Holmium holds the record for the highest magnetic moment of any naturally occurring element. It is used to concentrate the fields of the most powerful electromagnets. In medicine, its infrared laser shatters kidney stones and is used in prostate surgery.

Key facts

Atomic number: 67
Symbol: Ho
French name: Holmium
Atomic mass: 164.93 u
Molar mass: 164.93 g/mol
Family: Lanthanides
Position: period 6, f-block
State at 0 °C: Solid
Melting point: 1,460.9 °C
Boiling point: 2,599.9 °C
Density: 8.79 g/cm³
Electronegativity (Pauling): 1.23
First ionization energy: 581 kJ/mol
Atomic radius: 175 pm
Electron configuration: [Xe] 4f¹¹ 6s²
Abundance in Earth's crust: 1.3 ppm (56th most abundant element)
Indicative price: 57 $/kg (order of magnitude)
Radioactive: no
Discovery: 1878, Marc Delafontaine, Jacques-Louis Soret and Per Teodor Cleve

Origin of the name

From Holmia, the Latin name for Stockholm.

What does holmium look like?

A bright, soft, malleable silvery metal, fairly stable in dry air. Its oxide changes color with the lighting: yellowish in daylight, pink under fluorescent tubes.

Where is holmium found?

About 1.3 ppm of Earth's crust. It occurs in heavy rare-earth ores such as xenotime, gadolinite and ionic clays.

Natural sources

Xenotime
Gadolinite
Monazite
Ion-adsorption clays

How is holmium produced?

Separated from the other lanthanides by ion exchange or solvent extraction, then reduced from its fluoride with calcium. World production amounts to a few tens of tonnes a year.

Top producers

China
Myanmar

What is holmium used for?

Holmium-YAG lasers in urology (kidney stones, prostate).
Pole pieces that concentrate the field of powerful electromagnets.
Wavelength standard for calibrating spectrophotometers.
Radioactive holmium-166 microspheres against certain liver tumors.
Yellow or red colorant for glass and cubic zirconia.

In everyday life

Laser treatment of kidney stones in hospital
Colored cubic zirconia in jewelry

Role in living things

No known biological role.

Hazards of holmium

Low toxicity; metal dust is flammable.

Cosmic origin

Neutron stars: Created when two neutron stars collide — the “forge” of gold.

History of holmium

The Swiss chemists Marc Delafontaine and Jacques-Louis Soret spotted it by spectroscopy in 1878. In 1879 the Swede Per Teodor Cleve isolated its oxide from erbia and called it “holmia,” after Holmia, the Latin name for Stockholm.

Did you know?

In 2017, IBM researchers stored one bit of information on a single holmium atom.
Its laser emits at 2.1 micrometers, a wavelength strongly absorbed by water, which limits damage to nearby tissue.
It bears the Latin name of the Swedish capital.

Isotopes of holmium

Holmium has only one stable isotope, holmium-165. Surprisingly, its isomer 166m (an excited state of the nucleus) lives for more than a thousand years, far longer than ordinary holmium-166.

holmium-165: 100% of natural holmium, stable
holmium-166: radioactive, half-life 1.12 days. Injected as microspheres to irradiate liver tumors.
holmium-166m: radioactive, half-life 1,130 years. A long-lasting reference source for calibrating gamma detectors.

Related elements

Same family (lanthanides): Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu).