Assertion: protactinium's electron | /r/CapableOf | pack into inside orbitals
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Source sentences:
text: Each has 86 electrons arranged as in the atoms of the noble gas radon (which precedes actinium by three columns in the table), with three more electrons that may be positioned in the 6d and 7s orbitals (the seventh shell is outermost), and with additional electrons packing into inside orbitals.