Holmium (Ho)
“The element with the highest magnetic moment in nature — and the laser that shatters kidney stones without cutting the skin.”
How its electrons are arranged
Computed from the aufbau principle, with known real-world exceptions applied automatically.
Characteristics
- Electron configuration [Xe] 4f¹¹ 6s²; its chemistry is the steady +3 state of the lanthanides, with Ho³⁺ carrying [Xe] 4f¹⁰ under its bonds.
- Ho³⁺ holds the highest magnetic moment of any naturally occurring element — about 10.6 Bohr magnetons — making holmium a record-holder of the periodic table.
- Cooled towards liquid-helium temperatures the metal turns ferromagnetic, and chilled pole pieces of holmium concentrate magnetic flux into the strongest steady fields laboratories can build.
- Holmium oxide absorbs light in a comb of razor-sharp bands — so sharp that a holmium-glass filter serves worldwide as a wavelength calibrator for spectrophotometers.
A soft, silvery-white lanthanide that keeps its polish in dry air better than many neighbours, though moisture slowly dulls it. Its chemistry flashes yellow — holmium(III) oxide is a bright, buttery yellow, and Ho³⁺ salts wear soft yellow-pink tints.
Where you meet it
✦ Uses
- Ho:YAG surgical lasers firing 2,100-nanometre pulses down thin optical fibres — dusting kidney, bladder and ureter stones and shaving away overgrown prostate tissue with no incision at all.
- Flux-concentrator pole pieces: chilled near liquid-helium temperatures, holmium squeezes superconducting magnets into the strongest steady magnetic fields a laboratory can build.
- Holmium-166 microspheres, an emerging targeted radiotherapy that ferries radiation straight into liver tumours while sparing healthy tissue.
- Holmium-oxide glass filters — the quiet calibration standard that keeps UV-visible spectrophotometers reading wavelengths honestly.
◍ Everyday examples
- A urologist in a Dhaka hospital threading a laser fibre to dust a kidney stone is putting holmium’s 2.1-micrometre beam to work inside a living patient.
- Every properly calibrated laboratory spectrophotometer has had its wavelength scale checked against a holmium-glass filter’s fingerprint of sharp lines.
History & name
In 1878 the Swiss chemists Jacques-Louis Soret and Marc Delafontaine, working in Geneva, met an unexplained set of sharp spectral lines in rare-earth samples and announced a mystery “element X”. A year later, in 1879, the Swedish chemist Per Teodor Cleve pulled erbium oxide apart at Uppsala and found it concealing two new earths; one he christened holmia, after Holmia, the Latin name of his home city Stockholm — and it proved to be Soret and Delafontaine’s element X, giving the mystery lines a name at last.