Heavy nuclides progressively need a higher neutron content than the proton one as they get heavier. Heavy isotopes need an increasing content of neutrons to compensate the increasing content of protons. From the conventional standpoint this process should not present any limit since the neutron content could always be adjusted to overcome the increasing electrostatic repulsive forces from an increasing proton content. Furthermore, for a fix proton content the number of isotopes, i.e. the number of neutrons, should not be limited since these would not introduce repulsive forces.

From the orbital stand point this incoherence is straightly solved since nuclear neutrons, in dissociating, introduce two unitary opposite electric charges which generate two separated saturations. One is concerned with the positively charged proton core and the other one with the negatively charged bonding envelop. So, it turns out that the neutron content cannot be increased at will since its incorporation is electrically doubly active by rising at once the electric charge content of the core and of the envelop, and fattens the proton core up to a bonding threshold of the also fattening envelop. The threshold results from the non linearity of the balance from the repulsive electrostatic forces inner to the core and to the envelop and from their mutual attractive forces, finally leading to the exhaustion of the envelop ability to overcome the overall dispersive forces.

Fig.1.a: Orbital total cohesive energy v.s. proton content, for nuclides with odd mass from 247 to 265.

Fig.1.b: Orbital total cohesive energy vs. neutron content, for heavy isobars with odd mass from 247 to 265.

Figure 1.a shows that the orbital total energy for the heaviest isobars decreases all along the substitution of neutrons by protons. Instead figure 1.b shows its constant increase with the inverse substitution. In the orbital frame these behaviors take the following meanings. Since isobars only deal with their bonding envelop, the first behavior corresponds to the reduction of the envelop bonding carriers and hence of the total energy carried, and inversely for the second case. When nuclides are classified as isotones the varying weight within any given family only affects the core proton content. When classified as isobars the nucleus weight is thus constant within each family and hence only the wrapping orbital is affected by the substitution of protons by neutrons or vice versa. When classified as isotopes within each family both the core proton content and the wrapping orbital content of bonding carriers are affected at once through the content variation of neutrons, dissociated into their two components, proton and envelop. Here for the sake of conciseness only the case of heavy isobars will be considered.

Fig.2.a: Orbital energy per nucleon vs. proton content, for heavy isobars with odd mass from 247 to 265.

Fig.2.b: Orbital energy per nucleon vs. neutron content, for heavy isobars with mass from 257 to 266.

Figure 2.a shows the evolution of the mean orbital energy per nucleon (or equivalently core proton), for the last isobars with odd mass, showing its increment along with the substitution of protons by neutrons. This effect is easily understood considering that the substitution leaves the proton core unchanged but in contrast it reinforces the envelop carrier content. Inversely figure 2.b shows how the orbital energy per core proton decreases when neutrons are substituted by protons since this time for a proton core content equally constant, the envelop carrier content decreases and so does its cohesive capacity.

Fig.3.a: Orbital mean cohesive energy per neutron vs. proton content, for heavy isobars with mass from 257 to 266.

Fig.3.b: Orbital mean cohesive energy per neutron vs. neutron content, for heavy isobars with mass from 257 to 266.

Figure 3.a evidences the fall of the orbital energy per neutron, i.e. per bonding carrier along with the increment of neutrons, for isobars with mass from 257 to 266. Since the core is constant within each isobar family, the decrease of the envelop bonding of each nucleon would be lineal without the increasing repulsive forces inner to the envelop along with the increase of the carrier content.

Instead figure 3.b shows the orbital mean bonding energy per neutron along with the increment of conventional proton content, for the same isobars. Parallely the neutron content decreases since the core proton content remains constant. Consequently the total bonding energy is spread on a lower number of carriers, increasing thus the mean bonding energy carried by each one. However, the envelop total bonding energy does not remain constant along with the decrease of its carrier content, decreasing slightly. The non linearity of the increment of the bonding energy per carrier results thus to be due to the combined effects of the spreading of a progressively decreasing total bonding energy on a decreasing number of carriers.