Every atom consists of a complex structure divided into:
Nucleus: the part of the atom that contains the protons (positively charge) and neutrons (neutral charge). 99% of the mass of an atom is concentrated in the nucleus.
Electron cloud: the part that surrounds the nucleus where electrons are located (negatively charged particles); represented by the shape of the atomic orbitals.
Though it is believed that atoms are indivisible particles, they contain the following subatomic particles:
Protons: subatomic particles with a positive electric charge that determine the atomic number of the element.
Neutrons: subatomic particles with a neutral electric charge — that is, equal to zero — which makes them easy to penetrate and difficult to manipulate.
Electrons: subatomic particles with a negative electric charge; they represent less than 0.06% of the total mass of the atom and orbit around the nucleus.