Family
Unknown properties
This category gathers elements whose classification remains uncertain, mainly synthetic transactinides whose chemistry is known by extrapolation rather than direct measurement.
Element count
3
Z range
109–111
Dominant block
D
Transactinides (Rf to Og) are synthesised by heavy-ion collisions and often exist only as one or two atoms for a few seconds or milliseconds. Studying their chemistry requires unique 'one-atom-at-a-time' analysis techniques.
Some of them (Mt, Ds, Rg) still lack a consensus on their metallic behaviour or their precise place among the transition metals, hence their provisional classification as 'unknown properties'.