1. The positive particle in the nucleus of the atom is proton (4.)
2. An atom of an element that has different number of neutrons than the standard atom of that element is isotope (5).
3. The neutrally charged element in the nucleus of the atom is neutron (2).
4. The number of protons an atom has is an atomic number (3).
5. protons + neutrons in the nucleus of an atom is atomic mass (1).