It appears that you have some confusion about the particle physics inside the nucleus. Nothing "separates protons so that the strong force can hold the nucleus together", the strong force acts via the exchange of particles called mesons.
The atomic nucleus contains particles called protons and neutrons. The strong force binds the protons and neutrons together via the exchange of particles called mesons between those protons and neutrons.
The nucleus of an atom contains protons and neutrons, both of which are classified as baryons. Within all baryons are quarks, which are even smaller subatomic particles.
The particle not found in the nucleus is the electron
The nuclear particle that has no charge is the neutron.
nucleon
The small, negatively-charged particle in an atom is an electron. However, this is not in the nucleus. The small negative particles in the nucleus are down quarks, which are smaller than protons and electrons. Strange quarks and bottom quarks are also negative, but are not found in the nucleus.
A neutron is the subatomic particle that has no charge. It is found within the nucleus of atoms and contributes to the stability of the nucleus by balancing the positive charge of protons.
The particle not found in the nucleus is the electron
The Neutron and the Proton are to be found in the nucleus of an atom.
the electron
Protons and neutrons are found in the nucleus of an atom.
Protons and neutrons are found in the nucleus of an atom.
the electrons are found outside the nucleus. the nucleus contains protons and neutrons
electrons
proton
The nuclear particle that has no charge is the neutron.
neutrons and protons
nucleon
Neutron