During a laboratory activity, four students were given information about four unknown atoms. Answer the given questions.
| Atom | Number of Protons | Number of Neutrons | Number of Electrons |
| P | 17 | 18 | 17 |
| Q | 17 | 20 | 17 |
| R | 18 | 22 | 18 |
| S | 17 | 18 | 16 |
1. Which pair of atoms would have almost identical chemical properties? -
2. If atom S gains one electron, what will happen? -