They were once labeled group 0 in the periodic table because it was believed they had a valence of zero, meaning their atoms cannot combine with those of other elements to form compounds.
Neid nimetati kunagi perioodilisustabeli 0-rühmaks, kuna arvati, et nende valents on 0 ehk nende aatomid ei saa teiste elementidega ühendeid moodustada.