Main Question or Discussion Point
It seems odd to me that there would be a radioactive atom so far up the periodic table. What is it about this atom's atomic nucleus that makes it so unstable?
I have taken the German one and wrote a kind of summarization. Unfortunately the English site wasn't as detailed concerning the radioactivity of the isotopes. The good thing is, I learned something about the stability of nuclei myself.Did you check the Wikipedia page? It has a good introduction. There are several factors, mainly the very low energy of nuclei of elements nearby combined with the odd number of protons of technetium.
All (?) elements have radioactive isotopes.It seems odd to me that there would be a radioactive atom so far up the periodic table. What is it about this atom's atomic nucleus that makes it so unstable?
All (?) elements have radioactive isotopes. What is unusual is that elements 43 and 61 are the only elements with atomic number < 82 that have no stable isotope.It seems odd to me that there would be a radioactive atom so far up the periodic table. What is it about this atom's atomic nucleus that makes it so unstable?
As far as I can see it, the liquid-drop-model is - as quoted - semi-empirical, i.e. it takes the observations and tries to explain them by patterns. Those patterns represent the more general principle, that nature always tries to find local energy minima, stable points of balance where energy from elsewhere is needed to leave those states. Since all three atomic forces play a role here the overall situation can be pretty complex. The patterns mentioned in the liquid-drop-model are meant to reduce this complexity onto computational principles. And it works astonishingly well as I experienced as I took them to calculate 100-Tc as a preferred state.Is it pure random chance that elements 43 and 61 don't have any stable isotopes, or is there any more reason?
All the odd isotopes argon. scnr.The absence of stable odd isotopes of elements 18 and 58 is just as odd as their absence for elements 43 and 61.
Then why are 55 and 85 the preferred neutron numbers, seeing how both are odd?It is not that odd for the even-numbered elements - 37Ar would have 19 neutrons, 39Ar would have 21 neutrons. 20 is a magic number (the nuclear equivalent of noble gases - completed shells), so 37Cl and 39K are strongly bound, and the argon isotopes decay to those.
139Ce has 81 neutrons, 141 has 83. And 82 is a magic number again.
Magic numbers for reference: 2, 8, 20, 28, 50, 82, and 126
Technetium has no stable isotope because both 97 and 99 are unstable. For 97, the stable isobar is Mo, with 55 neutrons. For 99, the stable isobar is Ru, also with 55 neutrons. What´s special about 55 neutrons?Preferred in which way, and where do those numbers come from?