CHEMISTRY

Sharing the tiny crowded nucleus with every proton is another particle, the neutron. Neutrons are almost the same size and weight as protons, but they carry no electric charge at all. That single fact makes them the secret to nuclear stability. A nucleus packed with only positive protons would fly apart instantly, same charges repel. Neutrons slip between the protons and act as nuclear glue, letting the strong force bind everything together without any electrical fight. Without neutrons there would be no carbon, no iron, no oxygen, in fact no element past hydrogen would ever form.