What is radioactive disintegration, can u explain it plz?

It means that the nucleus of an atom is unstable and breaks down.The most known example is the disintegration(splitting)of the nucleus of the uranium 235 atom in the explosion of an atomic fission bomb,the 238 isotope of uranium is more stable.The cause of the instability seems to be connected to the balance of neutrons and protons that make up an atoms core,Even the isotopes of light elements like hydrogen can fission,for example hydrogen of m 1 or 2 are pretty stable but hydrogen of m 3 (called tritium) is very radioactive(the nucleus of one proton and two neutrons breks up rapidly).