ed ▁with ▁a ▁gas ▁containing ▁i od ine . ▁When ▁analyz ed ▁by ▁mass ▁spect rom etry ▁one ▁main ▁reaction ▁product ▁turns ▁out ▁to ▁be ▁. ▁These ▁clusters ▁of ▁ 1 3 ▁al umin ium ▁atoms ▁with ▁an ▁extra ▁electron ▁added ▁do ▁not ▁appear ▁to ▁react ▁with ▁o xygen ▁when ▁it ▁is ▁introduced ▁in ▁the ▁same ▁gas ▁stream . ▁Assuming ▁each ▁atom ▁liber ates ▁its ▁ 3 ▁val ence ▁electrons , ▁this ▁means ▁that ▁there ▁are ▁ 4 0   elect rons ▁present , ▁which ▁is ▁one ▁of ▁the ▁magic ▁numbers ▁noted ▁above ▁for ▁sod ium , ▁and ▁implies ▁that ▁these ▁numbers ▁are ▁a ▁reflection ▁of ▁the ▁noble ▁g ases . ▁Calcul ations ▁show ▁that ▁the ▁additional ▁electron ▁is ▁located ▁in ▁the ▁al umin ium ▁cluster ▁at ▁the ▁location ▁directly ▁opposite ▁from ▁the ▁i od ine ▁atom . ▁The ▁cluster ▁must ▁therefore ▁have ▁a ▁higher ▁electron ▁aff inity ▁for ▁the ▁electron ▁than ▁i od ine ▁and ▁therefore ▁the ▁al umin ium ▁cluster ▁is ▁called ▁a ▁super hal ogen . ▁The ▁cluster ▁component ▁in ▁ ▁ion ▁is ▁similar ▁to ▁an ▁i od ide ▁ion ▁or ▁better ▁still ▁a ▁b rom ide ▁ion . ▁The ▁related ▁ ▁cluster ▁is ▁expected ▁to ▁behave ▁chem ically ▁like ▁the ▁tri iod ide ▁ion . ▁ ▁Similarly ▁it ▁has ▁been ▁noted ▁that ▁ ▁clusters ▁with ▁ 4 2 ▁electrons ▁( 2 ▁more ▁than ▁the ▁magic ▁numbers ) ▁appear ▁to ▁exhib it ▁the ▁properties ▁of ▁an ▁al kal ine ▁earth ▁metal ▁which ▁typically ▁adopt ▁+ 2 ▁val ence ▁states .