Element: A substance consisting entirely from one type of atom, such as hydrogen or oxygen. It's like having a solar system with only one kind planet.
Electron Shell/Orbitals: The path or level where electrons revolve around an atom's nucleus. These are similar to specific orbits followed by planets in our solar system.
Nucleus (Atomic): The central part of an atom containing protons and neutrons; analogous to our sun in this mini solar system.