What atom is left when a nucleus disintegrates?

Answer 1

There are a number of possibilities as regards what happens when a nucleus "disintegrates" as was asked. There are a number of way that a nucleus can disintegrate, or change, so let's look at those. First there is spontaneous fission. You're familiar with fission because that's what happens in nuclear reactors, to name one thing. But in spontaneous fission, no neutron capture precedes the fission event. The atomic nucleus just "splits" on its own. Uranium, plutonium and a few other elements can do this, and there are a number of different possibilities as regards what fission fragments will result. Some unstable nuclei undergo what is called alpha decay. The nucleus dumps an alpha particle, which is actually a helium-4 nucleus, and is composed of a pair of protons and a pair of neutrons. There are a number of different alpha emitters known, and radon-222 is an example. It turns out that this isotope of radon appears when radium-226 undergoes alpha decay. In the event beta decay occurs, nuclear changes follow. There are two different types of beta decay, and they are beta plus decay and beta minus decay. An example is caesium-137, which will undergo a beta minus decay. It is sodium-22 that undergoes beta plus decay. As you can see, there are several different "disintegration modes" possible in nuclear decay. And there are basket full of possibilities when we look through them, so we can't list them all here. But we can give you links to each of these decay modes, and you'll find them below.