spin238Properties of the nuclide isotope Neptunium-238. Parent Nuclides. Direct parent isotope is: 242 Am. Nuclear Isomers. Nuclear isomers or excited states with the activation energy in keV relatedSpin; 238 Np: 2.099(2) d: 2+ Isotones and Isobars The following table shows the atomic nuclei that are isotonic (same neutron number N = 145) and isobaric (same nucleon number A = 238) with