Isotope is noted in an atomin name by the number following the Element which is always equal to the number of neutrons in a single atom of that isotope. Neutrons are the only particles that can be added or removed within an atom without changing the elemental properties. However, changing the isotope of a substance can alter more minor features. Changing the isotope of Uranium cannot make it a gas, but it can, for example make the Uranium more radioactive. When a particle is given more neutrons than the nuclear force can hold within the atom they begin to be released. Depending on the element, this process can take any amount of time from a few miliseconds to millions of years. This time of loss of neutrons is called a half-life and the process of losing particles is called decay. Isotopes that have this decay are known as Unstable Isotopes Unstable Isotopes usually decay untill they reach a point where they become stable again. However, some elements have no stable isotopes, and therefore will continue to decay, losing protons and electrons in the process creating a lighter, more stable element altogether.