Mendeleevium

Seven new elements were discovered with the 60-inch cyclotron: 85 (astatine), 93 (neptunium), 94 (plutonium), 96 (curium), 97 (berkelium), 98 (californium), and 101 (mendeleevium).

In 1960 the following transuranide elements were definitely known to exist (atomic numbers are given in parentheses): neptunium (93); plutonium (94); americium (95); curium (96); berkelium (97); californium (98); einsteinium (99); fermium (100); mendeleevium (101).[…]Element 101 — mendeleevium — was prepared in an even smaller quantity: 17 atoms in all.

The first dipositive actinide ion to be identified in aqueous solution was that of mendeleevium (262).[…]As mendeleevium is the analog of thulium, it was not surprising that nobelium, the analog of ytterbium, was subsequently found to form a very stable dipositive oxidation state.