The center of the atom is called the nucleus and contains the proton and neutron. The nucleus contains most of the mass of the atom, although its volume is much greater. There are usually the same number of protons and neutrons. When there are more neutrons than protons, the atom is called an isotope. The proton has a positive charge, the neutron no charge and the electron a negative charge.
Atoms have an atomic number.
This is the number of protons in the atom. The atomic weight of the atom is the sum of the protons and neutrons in the atom's nucleus. An atom is named by the element it represents. The electron orbits around the outside of the nucleus. In a neutral atom the number of electrons is the same as the atomic number, or the same as the number of protons.