It also tells us that chlorine has 18 neutrons (35 - 17) and, as the number of electrons and protons are equal in a neutral atom, chlorine also has 17 electrons. The relative mass of a nucleus is ...

Change the number of neutrons in an atom and it becomes an isotope, change the number of electrons, it becomes an ion. Radioactive decay - AQA With the wrong number of neutrons, nuclei can fall apart.

Instead, neutrons are held together inside an atom's nucleus solely by something called the strong force, one of the four fundamental forces of nature. As its name implies, the force is indeed ...