In the context of atomic structure, the space between an electron band (or energy level) and a proton is occupied by the electron cloud or electron orbitals. The electron cloud represents the probability distribution of finding an electron at a given position around the nucleus of an atom.
Electrons occupy specific energy levels or electron bands around the nucleus. These energy levels are often represented by shells, subshells, and orbitals. The innermost shell closest to the nucleus is filled first, followed by the subsequent shells.
Between the electron orbitals and the nucleus, there is a region known as the "atomic nucleus." The atomic nucleus is composed of protons and neutrons, which are tightly packed together due to the strong nuclear force. The protons carry positive charge, while the neutrons are electrically neutral.
The space between the electron orbitals and the atomic nucleus is primarily occupied by empty space or vacuum. However, it is important to note that the electron cloud is not a physically well-defined boundary, and electrons do not follow well-defined paths like planets around the Sun. Instead, the electron cloud represents the probability distribution of where an electron is likely to be found around the nucleus based on its energy level.