ChemicalElementsCrosswordPuzzleCluesDOWN1.Anunreactive,gaseouselementthatisaproductofthenuclearreaction(fusion)ofhydrogenatoms.Thisreactionoccurredatthebeginningoftimeandoccurstodayinstarssuchasoursun.Thesecondmostabundantelementintheuniverse,itisquiterareonEarth.Smallconcentrationsarefoundinsomenaturalgasdeposits.Itisuse...