The first atom, Hydrogen, is one proton and one electron, and the next, Helium, has two protons and two electrons but it also has two neutrons in its nucleus, and no-one knows why. Each higher element has not only another proton and electron, but also one or more neutrons, so:
“… all the stable nuclei have more neutrons than protons (or equal numbers), and the heavier nuclei are increasingly neutron-rich.” (Marburger, 2011), p254.
For some reason, heavier nuclei need more neutrons to be stable (Figure 4.22) but no theory can explain why. The shell model that explains electrons doesn’t work because some nuclei aren’t spherical. The standard model doesn’t help because if gluons hold the protons together, why have neutrons? And how do the gluons know how many neutrons a heavy nucleus needs to stabilize? Current models generally show the nucleus as protons and neutrons sitting side-by-side, like fruits in a bowl, with gluons forcing them together.
In the structure given earlier, protons and neutrons are quarks sharing photons in a closed triangle. This allows the triangles to open up and recombine in longer quark strings if the same rules are satisfied: namely a closed string with the internal angles of an equilateral triangle.
This suggests that a Helium nucleus isn’t proton and neutron particles sitting like fruit in a bowl, but a single quark string that closes back on itself when two protons and neutrons share photons.
In the fruit-bowl model, a Helium nucleus is separate proton and neutron particles held together but, in this model, it is one string of quarks held together by photon sharing. The only rule is that each link bends the string 60º, so quarks must rotate to connect. Higher nuclei then form in the same way.
This then explains why neutrons are needed. Protons can’t come close enough together to share photons because they repel, so neutrons have to act as buffers. When the nuclear quark string forms, neutrons sit between same-charge protons that can’t exist side-by-side, so there are at least as many neutrons as protons, as observed (Figure 4.22). For example, a Helium nucleus of two protons needs two neutron buffers between the protons in the closed string.
Closed quark strings will be compact and nearly spheres, as observed, but large nuclei may need more neutrons to avoid fold-back loci that happen to make protons adjacent. This nuclear evolution also makes some shapes more stable:
“Nuclei with either protons or neutron equal to certain “magic” numbers (2, 8, 20, 28, 50, 82, 126) are particularly stable.” (Marburger, 2011), p253.
If atomic nuclei are closed quark strings, they will fold in space to form shapes as proteins do. Those shapes that are symmetric will be more stable, so their nuclei numbers are the magic numbers that we see in symmetric shapes.
This model explains why atomic nuclei need neutrons while the fruit bowl particle model doesn’t.