Saw this statement over on wikipedia (http://en.wikipedia.org/wiki/Atom): “Each element has at least one isotope with an unstable nucleus”.
Is there some innate feature of atoms that makes this true? or have we just found it to be true with every element we’ve discovered so far?
One of the key indicators of stability is the neutron-proton ratio,so taking a stable isotope and adding or taking away a sufficient number of neutrons will create a an unstable isotope.
Yes, this is a fundamental characteristic of the nuclear force. Neutrons are needed in order for the attraction between protons to be stable. If you have too many neutrons or too few, the nucleus is unstable. Since an isotope can have any arbitrary number of neutrons, you can always specify an isotope that is unstable.
Here is an interesting plot. Stable isotopes are shown in black, and isotopes with half-lives too short to have ever been measured are shown in white. Atomic number (Z) is on the bottom, neutron number (N) on the left.
I see. So the “at least one” part refers to the number of protons or neutrons that can be removed.
Well, if you add or remove a proton you change which element it is.
In many ways it’s a very trivial observtion, because if you have an isotope with 500 neutrons in the nucleus, you know it will be incredibly unstable whatever element (though such an isotope would be for all intents and purposes impossible to create).
Indeed it is, and it is also quite an understatement, because as you can see from the linked chart, the vast majority of isotopes are unstable.
looks really cool in poster size.