Ferdinand-Frédéric-Henri Moissan first isolates fluorine by electrolyzing…

Ferdinand-Frédéric-Henri Moissan first isolates fluorine by electrolyzing a solution of potassium hydrogen fluoride (KHF2) in anhydrous hydrogen fluoride in 1886, using an apparatus constructed from platinum. (He will be rewarded with the Nobel Prize for chemistry in 1906.)

Also in 1886, Paul-Émile Lecoq de Boisbaudran obtains a relatively pure sample of the new rare earth Marignac had isolated from samarskite.

With Marignac's assent, they name the material gadolinia after gadolinite, the mineral in which the element occurs, itself named for Finnish chemist and mineralogist Johan Gadolin. (Gadolinium itself will be isolated only in comparatively recent times.)

The same year, Lecoq de Boisbaudran first finds element 66 associated with holmium and other heavy rare earths.

The element's name, dysprosium, derives from Greek dysprositos, difficult of access.