▁con den se ▁into ▁clusters , ▁prefer entially ▁containing ▁a ▁magic ▁number ▁of ▁atoms ▁( 2 , ▁ 8 , ▁ 2 0 , ▁ 4 0 , ▁ 5 8 , ▁etc .). ▁The ▁first ▁two ▁of ▁these ▁can ▁be ▁recognized ▁as ▁the ▁numbers ▁of ▁electrons ▁needed ▁to ▁fill ▁the ▁first ▁and ▁second ▁shell s , ▁respectively . ▁The ▁super atom ▁suggestion ▁is ▁that ▁free ▁electrons ▁in ▁the ▁cluster ▁occup y ▁a ▁new ▁set ▁of ▁orbit als ▁that ▁are ▁defined ▁by ▁the ▁entire ▁group ▁of ▁atoms , ▁i . e . ▁cluster , ▁rather ▁than ▁each ▁individual ▁atom ▁separately ▁( non - s pher ical ▁or ▁do ped ▁clusters ▁show ▁devi ations ▁in ▁the ▁number ▁of ▁electrons ▁that ▁form ▁a ▁closed ▁shell ▁as ▁the ▁potential ▁is ▁defined ▁by ▁the ▁shape ▁of ▁the ▁positive ▁nuc lei .) ▁Super at oms ▁tend ▁to ▁behave ▁chem ically ▁in ▁a ▁way ▁that ▁will ▁allow ▁them ▁to ▁have ▁a ▁closed ▁shell ▁of ▁electrons , ▁in ▁this ▁new ▁counting ▁scheme . ▁Therefore , ▁a ▁super atom ▁with ▁one ▁more ▁electron ▁than ▁a ▁full ▁shell ▁should ▁give ▁up ▁that ▁electron ▁very ▁easily , ▁similar ▁to ▁an ▁alk ali ▁metal , ▁and ▁a ▁cluster ▁with ▁one ▁electron ▁short ▁of ▁full ▁shell ▁should ▁have ▁a ▁large ▁electron ▁aff inity , ▁such ▁as ▁a ▁hal ogen . ▁ ▁Al umin ium ▁clusters ▁C ertain ▁al umin ium ▁clusters ▁have ▁super atom ▁properties . ▁These ▁al umin ium ▁clusters ▁are ▁generated ▁as ▁an ions ▁( ▁with ▁) ▁in ▁hel ium ▁gas ▁and ▁react