Atomic number 66

Dysprosium

Dy
+ phase
− phase

Shells Orbitals 4f 6s

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66 electrons in 6 shells: 2, 8, 18, 28, 8, 2.

Shells are a teaching model: an electron does not travel on a ring at a fixed distance.

Category: Lanthanide
Period: 6
Block: f
Standard atomic weight: 162.50(1) Da
Electron configuration: [Xe] 4f¹⁰ 6s²
Phase at 25 °C: solid
Melting point: 1407 °C
Boiling point: 2567 °C
Density: 8.55 g/cm³
Electronegativity (Pauling): 1.22
Discovered: 1886, Paul-Émile Lecoq de Boisbaudran

Neighbours in the table

Tb Ho

Hard to get at: that is the meaning of the Greek dysprositos, the word behind dysprosium’s name. The name recalls the struggle to separate it from a holmium mineral, in the history by CIAAW, the atomic-weights body of chemistry’s international union, IUPAC. The Swiss chemist Marc Delafontaine saw it first, in 1878, in the mineral samarskite, and called it philippia. Philippia was later taken for a blend of terbium and yttrium.

In 1886 the French chemist Paul-Émile Lecoq de Boisbaudran found the element again and received the credit. He found it in a holmium sample in CIAAW’s history, and as an impurity in erbia, erbium’s oxide, in Jefferson Lab’s account. Another French chemist, Georges Urbain, first isolated it in 1906, according to CIAAW. Only from 1950 were the oxide and the metal available in relatively pure form, on Los Alamos’s page, once Spedding and his associates developed ion-exchange separation and metallographic reduction.

There are 66 electrons in a dysprosium atom, sitting in shells of 2, 8, 18, 28, 8 and 2 and written [Xe] 4f¹⁰ 6s². Its oxidation state, a bookkeeping charge assigned as though every bond were ionic, is +3 in Jefferson Lab’s listing, and 3, 2 and 1 on Los Alamos’s page. The metal shines bright silver and is soft enough to cut with a knife.

Where it is found

Dysprosium makes up 5.2 milligrams of every kilogram of the Earth’s crust in Jefferson Lab’s figures, and seawater holds about 9.1 × 10⁻⁷ milligrams per litre. It occurs in xenotime, fergusonite, gadolinite, euxenite, polycrase and blomstrandine, according to Los Alamos. Its most important sources, though, are monazite and bastnäsite.

Monazite sand, with the formula (Ce, La, Th, Nd, Y)PO₄, is a phosphate rich in rare-earth elements, Jefferson Lab notes. Bastnäsite, a fluorocarbonate, was mined as a primary product at Mountain Pass in California, the US Geological Survey reports.

Natural dysprosium is a blend of seven isotopes. In CIAAW’s mole fractions, dysprosium-164 is the commonest of them at 28.26 per cent of the atoms. Dysprosium-162 follows at 25.48 per cent, dysprosium-163 at 24.90 per cent and dysprosium-161 at 18.89 per cent. The two lightest, dysprosium-156 and dysprosium-158, are each less than a tenth of a per cent.

Why it matters

Its heaviest natural isotope in CIAAW’s list gives dysprosium a place in nuclear reactors. Dysprosium-164 has a large neutron absorption cross section, a measure of how readily its nuclei capture neutrons. That is why dysprosium goes into control rods, in IUPAC’s isotope table. Los Alamos adds that its high melting point, with that neutron absorption, suggests uses in nuclear control and in alloys with special stainless steels. A dysprosium oxide-nickel cement has served in cooling reactor rods, Los Alamos reports. The cement absorbs neutrons readily and neither swells nor shrinks under long bombardment.

Two short-lived isotopes treat joints and tumours. Dysprosium-165 (half-life 2.332 hours in the Atomic Mass Data Center’s listing) is used in radiosynovectomy, an arthritis therapy, IUPAC notes. In that treatment, ferric oxide (iron(III) oxide) carrying dysprosium-165 is injected into the knee joint. Neutrons captured twice by dysprosium-164 make dysprosium-166, whose half-life is 81.6 hours in the evaluation of the International Atomic Energy Agency. It decays to holmium-166 and is used in cancer and arthritis therapy, IUPAC notes.

Dysprosium’s isotopes are highly magnetic, IUPAC notes, and physicists study how they interact and the structure of lattice supersolids. These are materials whose atoms sit in order yet flow without viscosity. Such experiments slow neutral atoms with laser light, called Doppler cooling, and hold them with magnetic quadrupole fields.

Properties

Properties of dysprosium Standard atomic weights from IUPAC/CIAAW (abridged, 2024); other values from PubChem's periodic table, kelvin converted to °C.
Property	Value	Unit	Source
Atomic number	66
Standard atomic weight	162.50(1) Da	Da	IUPAC/CIAAW 2024
Melting point	1407 °C	°C	Los Alamos: 1407 °C
Boiling point	2567 °C	°C	PubChem: 2840 K
Density	8.55 g/cm³	g/cm³
Electronegativity (Pauling)	1.22
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁰
Phase at 25 °C	solid

Safety

Dysprosium is a flammable solid in 60% of the 80 company reports giving a hazard class to the European Chemicals Agency, with the signal word Danger. Under the Globally Harmonized System (GHS), shares of 16 to 21% add that it may self-heat or ignite in air and release flammable gas with water. Similar shares list skin and eye irritation and lasting aquatic harm, while 25 of all 105 reports (23.8%) find it outside the hazard criteria. At room temperature the metal is relatively stable in air, Los Alamos notes, and handling guidance is in the PubChem Laboratory Chemical Safety Summary.

Questions

Is dysprosium radioactive?

Natural dysprosium is not. It has seven stable isotopes in Jefferson Lab's count, and the lightest of them, dysprosium-156, makes up about 0.056 per cent of the atoms in CIAAW's figures. Dysprosium-156 is stable for more than 10¹⁸ years in the listing of the Atomic Mass Data Center of the International Atomic Energy Agency (IAEA). Other isotopes do decay: dysprosium-159 has a half-life of 144.4 days, and dysprosium-154 one of about 3.0 million years, by alpha emission.

Does dysprosium have any commercial uses?

Few. Dysprosium has no commercial applications in Jefferson Lab's account. Reactor control rods and medicine do use it, in IUPAC's isotope table. Dysprosium has also gone into laser materials with vanadium and other rare earths, and dysprosium-cadmium chalcogenides have served as infrared sources for studying chemical reactions, Los Alamos reports.

How is dysprosium extracted?

Most dysprosium now comes from monazite sand through an ion exchange process, in Jefferson Lab's account. The metal can then be prepared by reducing dysprosium trifluoride, DyF₃, with calcium, according to Los Alamos. Small amounts of impurities can change its physical properties greatly, Los Alamos adds.

How much does dysprosium oxide cost?

Dysprosium oxide of at least 99.5 per cent purity cost an estimated 260 dollars a kilogram in 2024, in the US Geological Survey's Mineral Commodity Summaries. The average price was highest in 2021 of the five years USGS tabulates, at 410 dollars, then fell to 382 in 2022 and 330 in 2023. In 2020 it stood at 261 dollars, close to the 2024 figure.