Atomic nuclei consist of protons and neutrons. Protons and neutrons constitute the nuclei of atoms. Alpha particles are helium-4 nuclei (two protons and two neutrons). The atomic nucleus consists of protons and neutrons. The gluon holds together quarks to form protons and neutrons. It splits water into electrons, protons and molecular oxygen. Atoms are electrically neutral if they have an equal number of protons and electrons. Nuclides are composed of protons and neutrons. So the residuum from the strong interaction within protons and neutrons also binds nuclei together. Nuclear physics deals with how protons and neutrons arrange themselves in nuclei. The total number of protons and neutrons determine the nuclide. It consists of 8 protons and electrons, and 5 neutrons. "Bound" protons and neutrons, contained within an atomic nucleus, are generally considered stable. We can imagine ourselves building a nucleus by adding protons and neutrons. Lithium-4 contains three protons and one neutron.