Re: What would happen if a potassium atom was split?

Hi Trevor,

You asked what would happen if a potassium atom was split. From your studies of elements, you know that potassium contains 19 protons and (usually!) 20 neutrons. You may not have learned that it is also possible to find "isotopes" of potassium with either 21 or 22 neutrons, and that nuclear physicists can make isotopes with anywhere between 14 and 35 neutrons! But K39 (19p + 20n) is the common, interesting, stable isotope.

When you say "split" I presume you're talking about nuclear fission. Uranium, for example, undergoes fission in which the U235 nucleus falls apart into (typically) Barium and Krypton, and also discards a few neutrons. In general "all possible breakups are allowed" ... as long as you end up with the same number of protons (and neutrons) before and after your split, that is a "legal" fission process. So, you might imagine K39 breaking up into: H1 + Ar38, or He4 + Cl35, or Li7 + S32 ... and so on.

However, potassium-39 nuclei never break up on their own. A single K39 nucleus is more stable than any combination of things it might break into. (Unlike Uranium, for which a single U235 nucleus is less stable than almost any pair of nuclei smaller than it!) It is possible to break up potassium if you work really hard at it; high-energy particle collisions can break up any nucleus, by giving it lots of extra energy. In particular, you might be interested in "photodisintegration", a reaction in which a high-energy gamma ray (a photon) crashes into a nucleus and gives it enough energy to make "daughter" nuclei that are, put together, heavier than their parent. This and other photonuclear reactions can cause any of the different fission reactions described above. Remember, though, they do not happen naturally; they happen when you aim a beam of high-energy gamma rays at your brick of potassium.

What happens if you do split up the nucleus of a K39 atom? Well, you get two new nuclei, flying off in opposite directions at high speeds. Bumping into electrons as they go, they slow down and stop after going a few micrometers. As they travel they will acquire some electrons to orbit around them, and shortly after they stop (i.e. within microseconds) they will be ordinary, healthy, neutral atoms of the new element. (Perhaps these "daughter" atoms are radioactive, so they could undergo some other reaction at some point in the near future.) The electrons that were originally orbiting the K nucleus ... well, they'll be left behind when the daughter nuclei go zipping away. They'll drift off through the material, attach to various atoms temporarily, and eventually (probably within microseconds) find their way out of the material, or into the holes left by the stolen electrons.

So there's a whole Homeric epic drama among the electrons: they get left behind, stolen, lost, bumped into, they travel around making new acquaintances, etc.. This wreaks havoc with the chemical bonds in the area where all of this is going on; these damaged chemical bonds are collectively called "radiation damage"! That is why radiation is harmful, because it destroys chemicals (including important chemicals like DNA, ribosomes, antibodies, etc.)

Hope this helps. I couldn't find specific data on K photodisintegration, but you can spend some time at the sites linked above, or at other nuclear data centers, I'm sure you will find interesting things. One thing you will probably discover, is that it is much more common for photodisintegration to result in K39 --> H1 + Ar38, or K39 --> H2 + Ar37, than something like K39 --> F19 + Ne20. It's also possible, of course, to smash something into the nucleus so hard that the nucleus explodes into a shower of protons, neutrons, and other lightweight debris. That's what we particle physicists call heavy-ion collisions.

Hope this helps,

-Ben