Dysprosium wis first identified in 1886 bi Paul Émile Lecoq de Boisbaudran, but wis nae isolatit in pur fairm till the development o ion exchange techniques in the 1950s. Dysprosium is uised for its heich thermal neutron absorption cross-section in makin control rods in nuclear reactors, for its heich magnetic susceptibility in data storage applications, an as a component o Terfenol-D. Soluble dysprosium salts are mildly toxic, while the insoluble salts are considered non-toxic.
↑Yttrium and all lanthanides except Ce, Pm, Eu, Tm, Yb have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides". Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017.