The three parts of an atom are called protons, neutrons, and electrons.
Protons have a positive charge in an atom. The protons determine what type of element there is an it's the atomic number.
Neutrons have no charge in an atom. They are in the core of an atom along with the protons.
Electrons orbit the nucleus/core of an atom. The atomic number is the number of your protons and it is the number of electrons too.