That is, the analysis of the isotopic and chemical composition of the sample has far greater uncertainty than any uncertainty in the decay rate itself.The major reason that decay rates can change is that the electric field, from the atom's electron cloud, can change due to chemical changes.Historically, these are also known as alpha, gamma, and beta decays, respectively.
One key assumption is that the initial quantity of the parent element can be determined.
The Be nucleus (Beryllium-7) is an electron capturer with a half-life of about 53 days, turning into Lithium-7. While this half-life is way too short to be useful for radiometric dating, the effect of the chemical state is noticeable.
The reason is that, because the atomic number is only four, the 2s valence electrons are very close to the 1s electrons involved in capture.
In the case of carbon dating, it is not the initial quantity that is important, but the initial ratio of C, but the same principle otherwise applies.
Recognizing this problem, scientists try to focus on rocks that do not contain the decay product originally.