Per Teodor Cleve
Swedish chemist and geologist
February 10, 1840 - June 18, 1905

Cleve graduated from the University of Uppsala in 1863, and in 1874 became a professor at that same university. Cleve was interested in many branches of science, including chemistry, geology, botany and hydrography. He spent part of his later years making an extensive study of plankton.

Cleve continued the study of the rare earth erbia, from which the Swiss chemist Marignac had isolated ytterbium and scandium. He showed that erbia contained the oxides of three rare earth elements: erbium, holmium, and thulium. He studied the properties of cerium, lanthanum, and erbium. He predicted that didymium might contain another element, and this was later discovered by Welsbach (1885) and named neodymium. Holmium was named for Cleve's native city of Stockholm and the word thulium is derived from an old name for Scandinavia. Finally, the mineral cleveite is named in his honor.