| A | B |
|---|
| subatomic particle that contributes the least to the mass of an atom | electron |
| the mass of a proton | 1 |
| the charge of a proton | 1+ |
| the number of protons in the nucleus of 15P32 | 15 |
| the mass number of an ion that consists of 20 protons, 20 neutrons, and 18 electrons | 40 |
| mass number of an atom is equal to | protons plus neutrons |
| has a mass 1/1837 of the mass of a proton | electron |
| a Na atom has more of these than a Na+ ion | electrons |
| number of protons in an OH- ion | 9 |
| maximum number of electrons in the 3rd energy level | 18 |
