^{4}\textrm{He}\) When a radioactive atom emits an alpha particle the mass number decreases by four and the atomic number drops by two. Here is the equation for the alpha decay of radon-219 into ...

Certain isotopes are unstable and undergo a process of radioactive decay, slowly and steadily transforming, molecule by molecule, into a different isotope. This rate of decay is constant for a ...

Save guides, add subjects and pick up where you left off with your BBC account. Radioactive decay is a spontaneous and random process. A block of radioactive material will contain many trillions ...