▁are ▁very ▁strong ▁ox id izing ▁agents . ▁Like wise ▁the ▁common ▁ox id ation ▁state ▁for ▁gold ▁is ▁+ 3 , ▁which ▁pre cludes ▁there ▁being ▁much ▁common ▁chem istry ▁between ▁mer cur y ▁and ▁gold , ▁though ▁there ▁are ▁similar ities ▁between ▁mer cur y ( I ) ▁and ▁gold ( I ) ▁such ▁as ▁the ▁formation ▁of ▁linear ▁d icy ano ▁complex es , ▁[ M ( CN ) 2 ] − . ▁According ▁to ▁I UP AC ' s ▁definition ▁of ▁transition ▁metal ▁as ▁an ▁element ▁whose ▁atom ▁has ▁an ▁incomplete ▁d ▁sub - shell , ▁or ▁which ▁can ▁give ▁rise ▁to ▁c ations ▁with ▁an ▁incomplete ▁d ▁sub - shell , ▁z inc ▁and ▁cad m ium ▁are ▁not ▁transition ▁met als , ▁while ▁mer cur y ▁is . ▁This ▁is ▁because ▁only ▁mer cur y ▁is ▁known ▁to ▁have ▁a ▁comp ound ▁where ▁its ▁ox id ation ▁state ▁is ▁higher ▁than ▁+ 2 , ▁in ▁mer cur y ( IV ) ▁flu or ide ▁( though ▁its ▁existence ▁is ▁disput ed , ▁as ▁later ▁experiments ▁trying ▁to ▁confirm ▁its ▁synth esis ▁could ▁not ▁find ▁evidence ▁of ▁H g F 4 ). ▁However , ▁this ▁classification ▁is ▁based ▁on ▁one ▁highly ▁at yp ical ▁comp ound ▁seen ▁at ▁non - equ ilib rium ▁conditions ▁and ▁is ▁at ▁odd s ▁to ▁mer cur y ' s ▁more ▁typical ▁chem istry , ▁and ▁J ensen ▁has ▁suggested ▁that ▁it ▁would ▁be ▁better ▁to ▁regard ▁mer cur y ▁as ▁not ▁being