Practice Questions
| 1. | Discovery of subatomic particles Difficulty: easy | 
                                    
                                    3
                                 | 
| 2. | Calculate the number of electrons and protons I Difficulty: medium | 
                                    
                                    2
                                 | 
| 3. | Calculate the number of electrons and protons II Difficulty: medium | 
                                    
                                    3
                                 | 
| 4. | Find the number of electrons in ions Difficulty: medium | 
                                    
                                    4
                                 |