curium

Curium was the third transuranium element to be discovered. The first isotope of this element was the isotope, Cm²⁴², which was identified by G. T. Seaborg, R. A. James and A. Ghiorso at the Metallurgical Laboratory as the result of its production in the Berkeley cyclotron […] The availability of this isotope of curium made it possible to study the chemical properties of this element by the use of the tracer technique. Extensive investigations have led to the conclusion that curium probably exists exclusively in the III oxidation state in aqueous solution.

1946 November 18 (date delivered), Glenn T[heodore] Seaborg, Plutonium and Other Transuranium Elements (MUC-1780; MDDC (Manhattan District Declassification); no. 505), Oak Ridge, Tenn.: United States Atomic Energy Commission, →OCLC, page 8

The chemical properties of americium and curium may be summarized in the statement that they bear a striking resemblance to the rare earth elements, particularly those of atomic numbers 60 to 64. […] Thus the chemical properties of americium and curium support the view that these elements are members of an actinide series in which the 5f electron shell is being filled just as the 4f shell is being filled in the rare earth series. Curium is believed to possess seven 5f electrons just as gadolinium possesses seven 4f electrons.

1948 January 21, S[tanley] G[erald] Thompson, R[alph] A[rthur] James, L. O. Morgan, The Tracer Chemistry of Americium and Curium (AECD-1907), Oak Ridge, Tenn.: Technical Information Division, Oak Ridge Directed Operations, United States Atomic Energy Commission, →OCLC, page 1