, ▁like ▁sil icon ▁above ▁it , ▁is ▁an ▁important ▁sem icon duct or ▁and ▁is ▁commonly ▁used ▁in ▁di odes ▁and ▁trans ist ors , ▁often ▁in ▁combination ▁with ▁ar sen ic . ▁German ium ▁is ▁fairly ▁rare ▁on ▁Earth , ▁leading ▁to ▁its ▁compar atively ▁late ▁discovery . ▁German ium , ▁in ▁comp ounds , ▁can ▁sometimes ▁ir rit ate ▁the ▁eyes , ▁skin , ▁or ▁l ungs . ▁ ▁Ar sen ic ▁ ▁Ar sen ic ▁( As ) ▁is ▁an ▁element ▁in ▁group   1 5 . ▁Ar sen ic , ▁as ▁mentioned ▁above , ▁is ▁often ▁used ▁in ▁sem icon duct ors ▁in ▁allo ys ▁with ▁g erman ium . ▁Ar sen ic , ▁in ▁pure ▁form ▁and ▁some ▁allo ys , ▁is ▁incred ibly ▁poison ous ▁to ▁all ▁mult ic ell ular ▁life , ▁and ▁as ▁such ▁is ▁a ▁common ▁component ▁in ▁p estic ides . ▁Ar sen ic ▁was ▁also ▁used ▁in ▁some ▁p ig ments ▁before ▁its ▁to x icity ▁was ▁discovered . ▁ ▁S elenium ▁ ▁S elenium ▁( Se ) ▁is ▁an ▁element ▁in ▁group   1 6 . ▁S elenium ▁is ▁the ▁first ▁non met al ▁in ▁period   4 , ▁with ▁properties ▁similar ▁to ▁sul fur . ▁S elenium ▁is ▁quite ▁rare ▁in ▁pure ▁form ▁in ▁nature , ▁mostly ▁being ▁found ▁in ▁min er als ▁such ▁as ▁py rite , ▁and ▁even ▁then ▁it ▁is ▁quite ▁rare . ▁S elenium ▁is ▁necessary ▁for ▁humans ▁in ▁trace ▁amounts , ▁but ▁is ▁to