This makes it the heaviest atom commonly found in nature. Uranium turns blue in air because it develops an oxide coating. The biggest deposits of uranium ore are at Blind River, Canada, in South Africa, Australia, France, and in Colorado and Utah in the United States. Inside the elements Chemistry is concerned with the exchange or sharing of electrons in the outside regions of an atom, rather than with what happens in the core of an atom, in the nucleus. However, when working with radioactive elements, scientists, need to understand the nature of the particles that make up the atoms.
Radioactive elements vary greatly.
Indeed, if used this way they could make rather dangerous materials. Rather, radioactive elements are used for their radioactive properties alone. Because like charges repel each other, there is always a force trying to push the protons apart. Provided there are not too many protons in the nucleus, other forces can hold the protons together. But if the ratio of protons to neutrons is not within certain limits, protons may not be held firmly together, and they form an unstable nucleus.