Disintegration processes of materials
Friction force and other negative environmental conditions cause all materials to disintegrate into smaller particles (molecules, atoms or ions) in certain period of time. Those particles distribute in environment in various ways and make various compounds with other particles or their groups. Everything happens progressively: at first materials disintegrate into smaller parts of the same composition, later - into even smaller particle groups and etc. Gradually they disintegrate into individual particles - molecules or complex ions. Later they decompose into individual atoms and non-complex ions. After even larger period of time, the cores of those atoms and ions split and emit radioactive rays (this creates other kinds of atoms and ions, which differ from the previous ones in their composition). Radioactive materials are composed from atoms with very weak structure, so, they are extremely fragile and split very quickly under the influence of environmental conditions and for that reason it is considered that the cores of those atoms split spontaneously.
