| A | B |
|---|
| proton | a positive particle in the nucleus with a mass of 1 AMU |
| neutron | a particle in the nucleus with NO charge and a mass of 1 AMU |
| electron | negatively charged particles with no apparent mass |
| atomic number | the number of protons in the nucleus of an atom |
| isotopes | atoms that have the same number of protons but different numbers of neutrons |
| mass number | the sum of protons and neutrons in an atom |
| atomic mass | the average of masses of all isotopes of an element |
| atomic mass unit | the scientific unit which expresses the masses of the particles in atoms |
