Page "Rutherfordium" Paragraph 11

The chemical properties of rutherfordium were based on calculation which indicated that the relativistic effects on the electron shell might be strong enough that the p orbitals have a lower energy level than the d orbitals, therefore making the element behave more like lead.

With better calculation methods and studies of the chemical properties of rutherfordium compounds it could be shown that rutherfordium behaves according to the rest of the group 4 elements.