Neptunium charge state

Much work has been done on the charge states of neptunium following alpha decay in various americium compounds and frozen solutions. 

A tabulation of some of these results shows that only the + 3 state of neptunium is observed in frozen solutions, whereas in the pure solid a range of values from +3 to +5 is observed, which is independent of the charge state of the americium in the parent compound. An interesting comparison for K5[Am 02(C03)s]3 in the pure solid and in frozen solution indicates the existence of Np + alone in the pure solid and only Np in the frozen solution. This suggests that the presence of ice at low temperatures provides a reducing medium for neptunium. 

A radiochemist isolates 8.6 /ng of a chloride of neptunium (atomic weight = 237 g/mole), which she proves has the formula NpCl3. in trying to find the possible valence states of Np, she finds that titration of the 8.6 /xg sample requires 37.5. 1 of 0.00200 N KMn04 solution. To what electrical charge must the Np have been oxidized ... 

The chemical isomer shifts decrease considerably as the formal oxidation state of the neptunium increases from +3 to +6. Comparison of the shifts with electron charge densities at the nucleus derived from non-relativistic Hartree-Fock wavefunctions for 5/ to 5/ configurations showed a linear interrelationship. An approximate value for d<7 >/ of —3-5 X lO" was derived. 

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