The nucleus of an atom is made up of two subatomic particles: the proton and the neutron.
Atoms constitute the main building blocks of matter and they are made up of smaller subatomic particles consisting of a nucleus surrounded by electrons.
In the nucleus, the proton is electrically charged, carrying a relative positive charge but the neutron carries no electric charge and it is neutral. The nucleus is surrounded by electrons which carry a negative charge and they are arranged in shells or energy levels around the nucleus.
The atomic number of an atom is the number of protons in the nucleus and atoms are arranged in the periodic table in the order of their atomic number. Atoms do not have an overall electric charge because the number of electrons (carrying negative charges) in the atom is the same as the number of protons in the atom (carrying positive charges) in the ground state.