2 2 . ▁The ▁ 8 s ▁and ▁ 8 p 1 / 2 ▁orbit als ▁are ▁predicted ▁to ▁be ▁so ▁strongly ▁stabil ized ▁relativ ist ically ▁that ▁they ▁become ▁core ▁electrons ▁and ▁do ▁not ▁particip ate ▁in ▁chemical ▁re actions , ▁unlike ▁the ▁earlier ▁group ▁ 1 2 ▁elements ▁where ▁the ▁s ▁electrons ▁behave ▁as ▁val ence ▁electrons . ▁However , ▁the ▁ 9 s ▁and ▁ 9 p 1 / 2 ▁levels ▁are ▁expected ▁to ▁be ▁readily ▁available ▁for ▁hy brid ization ▁and ▁bond ing , ▁so ▁that ▁un hex quad ium ▁should ▁still ▁behave ▁chem ically ▁like ▁a ▁normal ▁transition ▁metal . ▁Calcul ations ▁predict ▁that ▁the ▁ 7 d ▁electrons ▁of ▁un hex quad ium ▁should ▁particip ate ▁very ▁readily ▁in ▁chemical ▁re actions , ▁so ▁that ▁un hex quad ium ▁should ▁be ▁able ▁to ▁show ▁stable ▁+ 6 ▁and ▁+ 4 ▁ox id ation ▁states ▁in ▁addition ▁to ▁the ▁normal ▁+ 2 ▁state ▁in ▁a que ous ▁solutions ▁with ▁strong ▁lig ands . ▁Un hex quad ium ▁should ▁thus ▁be ▁able ▁to ▁form ▁comp ounds ▁like ▁U h q ( CO ) 4 , ▁U h q ( PF 3 ) 4 ▁( both ▁t etra hed ral ), ▁and ▁ ▁( linear ), ▁which ▁is ▁very ▁different ▁behavior ▁from ▁that ▁of ▁lead , ▁which ▁un hex quad ium ▁would ▁be ▁a ▁heav ier ▁hom olog ue ▁of ▁if ▁not ▁for ▁relativ istic ▁effects . ▁Nevertheless , ▁the ▁div al ent ▁state ▁would ▁be ▁the ▁main ▁one ▁in