| A | B |
|---|
| electrons | negatively charged particles found in clouds outside the nucleus |
| protons | positively charged particles in the nucleus |
| neutrons | particles in the nucleus with a neutral charge |
| nucleus | the positively charged center of the atom made up of protons and neutrons |
| atomic mass unit | the mass of one proton or neutron |
| atomic number | the number of protons in the nucleus |
| mass number (atomic weight) | the sum of protons and neutrons in an atom |
| determining number of neutrons | subtract the atomic number from the mass number |
| atomic mass | the average of the masses of all the isotopes |
