# Does radioactivity affect chemical reactions?

Do compounds of radioactive elements show a different behaviour? What happens when the radioactive part of the given compound decays? e.g. Radium chloride; what happens to it when radium decays?

• As pure speculation I assume the compound falls apart. The chemical bonding is related to the number of electrons around an atom, and number of electrons is related to number of protons. Let's say an atom goes through alpha decay and loses 2 protons, this changes the charge balance and might disrupt the chemical bonding. If I had sources I'd try to make an answer. – user137 Dec 8 '14 at 16:46
• @tschoppi Radioactive decay can be used to intentionally trigger reactions. – Nicolau Saker Neto Dec 9 '14 at 15:42

During the nuclear reaction, the atomic number Z (and therefore chemical identity) changes (transmutation). In your example, $\ce{RaCl_2 -> \alpha^{2+} + RnCl_2^{2-} -> He + RnCl_2}$.

Radon being noble gas would react further, e.g. $\ce{RnCl_2 -> Rn + Cl_2}$

If the decaying atom would be a transition metal with ligands, it's properties should not change so drastically so that the ligands will stay attached.

• poor answer, the recoil energy when a decay occurs can break bonds cause other changes to occur. – Nuclear Chemist Mar 17 '19 at 16:41

I'd like to add to the other answers. Although not directly an answer to your question, I do feel it's relevant. Radioactive decay can cause damage to crystalline solids.

Take the example of apatite $\left(\ce{Ca5[PO4]3[F,Cl,OH]}\right)$, which can host a bit of uranium in the crystal structure. When this uranium decays, the resulting particle damages the host crystal. The crystal can then be polished and etched to reveal these so called "fission tracks":

Heating of a damaged crystal will cause the damage to "heal" and the tracks to disappear. Thus, radioactive decay can indirectly induce chemical reactions. This routinely occurs in the deep Earth. It also has some very useful applications in geochronology, which you can read about in the Wikipedia article about fission tracks.

I think we need to avoid concetrating too much on the atom at which the decay occured, it is true that many radioactive decays will cause bonds to break as a result of the recoil energy. But alpha, beta and gamma radiations coming from the radioactive atom can deposit energy in the solution, liquid, gas or solid where the radioactivity is present and thus cause chemical reactions to occur.

If you irradate water then the first products are the solvated electrons and H2O cations, these can then react to form a range of reactive species such as HO and H radicals. These can then react further to give things like hydrogen gas and hydrogen peroxide. All of these reactive species can cause chemical reactions to occur.

It is interesting that a solution of a radioactive chemical will undergo autoradiolysis which can change the chemical form of the radionuclide. For example if I was to start with a concentrated plutonium solution in the +6 oxidation state in an aqueous solution. Then if I was to seal it up then the radiation could cause the formation of other oxidation states of Pu, so I would soon end up with a mixture of Pu(III), Pu(IV), Pu(V) and Pu(VI). It is possible with additves to try to control the oxidation state of the plutonium (or other metal), so in some systems the chemistry can be tamed.

In addition to radioactive decay, which would, in the case of radium, give radon and an alpha particle (helium nucleus) that will strip 2 electrons from chloride ions or anything else nearby, the radioisotope will have a different mass from the stable isotope. This in turn may affect its reaction rate . The so-called isotope effect is largest in the case of hydrogen (tritium being the radioactive and three times heavier isotope, and it reacts slower in reactions involving the C-H bond.

• What about the fundamentally different chemical reactivities of the decay products? I fail to see how this question has anything to do with isotope effects. – tschoppi Dec 8 '14 at 23:33
• One part of the question was do radioactive compounds show a bit different behavior. Isotope effects are part (but not all) of the answer. – iad22agp Dec 8 '14 at 23:37
• I am not asking about reactions they show, but their properties How would example of NaCl (sodium-24, half life 15 hours) follow. – user10153 Dec 9 '14 at 14:28
• Until the moment a radioactive isotope decays, it behaves like a stable isotope. You do not seem to be asking about how the radioisotope differs up until the moment of decay, and yet after it decays, it is now a different element. Looks like some of the other forum members have covered it pretty well by now. – iad22agp Dec 9 '14 at 22:32