Most accurate form of radiometric dating
That is, electrons can move closer to or farther away from the nucleus depending on the chemical bonds.
This affects the coulomb barrier involved in Alpha decay, and therefore changes the height and width of the barrier through which the alpha particle must tunnel.
In fact, it is possible to shut down electron capture completely—simply ionize the substance so that there are no electrons nearby.
There is a fairly well-known example of chemical state affecting electron capture activity.
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.The effect of this on alpha decay, which is the most common decay mode in radiometric dating, is utterly insignificant.There is another effect that takes place in the "electron capture" type of Beta decay.This is an example of the Weak force, and is fairly rare.Electron capture requires that there be an electron in the vicinity of the nucleus, so its activity depends strongly on the configuration of the electron cloud, which depends on the chemical state.