2 + ▁and ▁Ag Ar n 2 + ▁for ▁n = 1 - 8 , ▁with ▁a ▁peak ▁occurrence ▁of ▁Cu Ar 4 2 + , ▁or ▁Ag Ar 4 2 + , ▁and ▁Au Ar n 2 + ▁n = 3 – 7 . ▁ ▁In ▁addition ▁to ▁the ▁four ▁arg on ▁atoms , ▁the ▁six ▁arg on ▁atoms ▁clusters ▁have ▁en hanced ▁concentration . ▁The ▁stability ▁of ▁the ▁ ions ▁with ▁two ▁positive ▁charges ▁is ▁unexpected ▁as ▁the ▁ion ization ▁energy ▁of ▁arg on ▁is ▁lower ▁than ▁the ▁second ▁ion ization ▁energy ▁of ▁the ▁metal ▁atom . ▁ ▁So ▁the ▁positive ▁second ▁charge ▁on ▁the ▁metal ▁atom ▁should ▁move ▁to ▁the ▁arg on , ▁ion izing ▁it , ▁and ▁then ▁forming ▁a ▁highly ▁rep uls ive ▁mole c ule ▁that ▁under go es ▁a ▁C oul omb ▁explos ion . ▁However ▁these ▁mole cules ▁appear ▁to ▁be ▁k inet ically ▁stable , ▁and ▁to ▁transfer ▁the ▁charge ▁to ▁an ▁arg on ▁atom , ▁they ▁have ▁to ▁pass ▁through ▁a ▁higher ▁energy ▁state . ▁The ▁clusters ▁with ▁four ▁arg on ▁atoms ▁are ▁expected ▁to ▁be ▁square ▁plan ar , ▁and ▁those ▁with ▁six , ▁to ▁be ▁oct ah ed ral ▁dist orted ▁by ▁the ▁Jah n - T eller ▁effect . ▁ ▁Poly atomic ▁an ions ▁▁ ▁Ex amples ▁of ▁an ions ▁containing ▁strong ▁b onds ▁with ▁noble ▁g ases ▁are ▁extremely ▁rare : ▁generally ▁nucle oph il ic ▁nature ▁of ▁an ions ▁results ▁in ▁their ▁in ability ▁to ▁bind ▁to ▁noble