Radioactivity is not affected by chemical reactions or any change in physical conditions, such as temperature, pressure, electric fields or magnetic fields and etc.
ALL the nuclei of a radioactive substance have the same probability of undergoing radioactive decay (by emitting alpha, beta or gamma particles). It is IMPOSSIBLE to tell which nuclei will be the next in line to decay or how long it will take to decay.
Since it is independent of external conditions and the breakdown within the nucleus is completely random, i.e., occurrence of radioactive emission is random over space and time.
But, it is noticed that with many repeated observations of the random process, the average of its radioactive emissions does follow some statistical laws. You can calculate approximately how much of a “basket” of radioactive materials will decay in X time.