Nucleus Contains protons and neutrons Makes up most of the mass of an atom. Small part of atoms volume. Electron Cloud Space in which electrons orbit the nucleus at high speed. Large part of atoms volume. Subdivided into Energy Levels or Shells.
Electrons occupy the lowest energy levels.
This table shows the maximum number of electrons for the first 4 energy levels . Energy Level Max. This table shows the electron shell configuration for the first 18 elements. The number of protons in the atom. Element Consists of atoms all having the same atomic numbers.