Neutrons in the Nucleus. I

It is supposed that the nucleus consists of $\alpha$-particles, neutrons and zero or one proton, instead of the former structure scheme, $\alpha$-particles, electrons and 0, 1, 2, 3 protons. The calculated mass defects $\Delta m$ of the isotopes of a single element show an exact linear increase of $\Delta m$ with the mass number (instead of the fluctuating function in the former structure scheme). The $\Delta m$-difference of the isotopes of each element is rather constant throughout the periodic system for even elements. The absolute values of the mass defects give a potential energy curve decreasing uniformly with increasing atomic number (instead of showing a minimum at the element No. 50 in the former structure scheme). In the region of the radioactive substances the energy curve seems to turn up again. All of this helps the model that the isotopes of an element differ only by the number of neutrons incorporated by them, the binding energy per neutron being rather constant throughout the periodic system and about 0.009 in mass units for even elements. In several cases the isotopes give a picture of the construction of a complete outer shell of 8 or 12 neutrons and indications that also in other cases there is a shell structure of the neutron arrangement, but none of the $\alpha$-particles. The empirical rule that odd elements have no isotopes with even mass numbers can be explained, together with its exceptions, by help of the neutron structure scheme.