Who isolated scandium oxide in late 1879, confirming eka-boron?

Lars Fredrik Nilson isolated scandium oxide in late 1879, confirming the identity of Mendeleev’s eka-boron.

Nilson discovered the new element while analyzing the rare-earth minerals euxenite and gadolinite. He separated a high-purity oxide, later called scandia, and spectral analysis revealed previously unreported lines. He named the element scandium, from Scandia, the Latin name for Scandinavia.

The confirmation involved more than one scientist. Nilson made the chemical discovery, while Per Teodor Cleve recognized that scandium’s properties matched Mendeleev’s earlier prediction of eka-boron and communicated the connection to Mendeleev. Mendeleev had predicted an atomic mass of about 44 in 1871; scandium’s standard atomic weight is approximately 44.96.

The main distractor confusion concerns Paul-Émile Lecoq de Boisbaudran, who discovered gallium, the element corresponding to eka-aluminium. Carlo Perrier, together with Emilio Segrè, discovered technetium much later, while Clemens Winkler discovered germanium, corresponding to eka-silicon.