The first rare earth element yttrium was discovered by Johan Gadolin in 1794. In 1839, the Swedish C.G. Mosander discovered a mixture of lanthanum and praseodymium (didymium).After this, chemists in various countries paid special attention to the separation of new elements from the rare earth elements that have been discovered.In 1885, the Austrian A.V. Welsbach discovered praseodymium and neodymium from a mixture of praseodymium and neodymium that Mosundel considered to be "new elements". One of them was named neodymium, which was later simplified to neodymium. The element symbol Nd is neodymium. The last rare earth element promethium Pm was discovered by J.A.Marinsky, L.E.Glendenin and C.E.Coryell in 1947.