Atomic radii

  • Thread starter elas
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  • #26
Originally posted by elas
Alexander
Appreciate your help and understand your reply but I am looking for the origin of what at present appears to be an assumption.
Given that the electron orbit is determined by magnetic force, why should the addition of a neutral particle alter the orbit but, as mass is being added, why should the volume remain the same?
This can of course be explained as an increase in density but I cannot find any reference to such an increase and even and if I accept a change in density and no change in radii this begs the question 'why does a change in density not alter the electron orbit'?
Given that some isotopes are radioactive (when their associated element is not); clearly there are occassions when the addition of a neutron does alter the magnetic relationship.
If a hydrogen atom was the size of a football field, the proton would be the size of (roughly), a pea. If you put another pea in the field you've doubled the mass but the football field doesn't get any bigger.

You've answered your own second question. The size of an electron's orbit is measured by the electomagnetic force, the mass of the nucleus doesn't have anything to do with it. I don't see the source of your confusion.

What do unstable nuclei have to do with the electromagnetic force and orbitals?
 
  • #27
elas
Your analogy is poor, remove all the footballs and you still have an unchanged football field; remove all the nucleons and there is no atomic field. Regardless of the difference in size the atomic field is part of the nucleons and as the nucleons decrease so does either the field radii and/or the mass.
If the Earth escaped from the gravitational field of the sun it would take the Earth's gravity field with it; but you cannot say that an atom's field is a distortion of spacetime without saying spacetime is magnetic and clearly that is ridiculous. The alternative is that nucleons take something with them when they leave. That is only possible if you think in terms of force fields and not solid objects such as footballs.
 
  • #28
Alexander
elas, do you know what isotop is and what element is?

Do you know, for example, what is the difference between U238, U235, Pu238, Pu235?
 
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  • #29
elas
Three neutrons!, but it seems the difference between element and isotope is really a matter of commonality and that is hardly a good scientifc reason for giving things different names. In reality they are atoms and is is by taking all atoms (element or isotope) into one table that we see the fundamental structure of all atoms.
The beauty of ignoring clasification and using an all atoms table is that it is then possible to see the structural link between atoms and sub-atomic particles and also between mass and waves. The only problem is the tedious work of writing up the tables, but I have done enough to see that I am on the right track.
I realise that I lack the training to explain myself in the proper terms, that willl come out in the wash, the beauty is in the simplicity of the numbers and I hope to get to the end soon.
 
  • #30
Alexander
Ok, so all isotopes of the same elment have SAME number of protons, thus SAME electric field everywhere (except small difference inside nucleus), thus SAME conditions for electrons. Thus, electrons in these similar condidions behave similar (=have SAME wave function for all isotopes of SAME element). Thus radii of all isotopes of the same element are SAME.
 
  • #31
elas
So how do you allow for the difference in mass?
 
  • #32
damgo
You use the reduced mass, m_e*m_nucleus/(m_e+m_nucleus) . Since the electron is so much lighter than the nucleus, this is a very small correction; and so the correction for different isotopes is a *very*-small second-order effect. Even for say hydrogen vs. tritium, where it will be most noticeable, you get

hydrogen: m_e*(1-0.00054)
tritium: m_e*(1-0.00018)
 
  • #33
elas
I agree the difference is very small, but I found a method of determining the difference in radius caused by this small difference in mass. When I tried to discover if I had something new I was met with several replies stating that there is no change in radius. I still have not had any authoritive reference for this claim.
Meanwhile I am continueing with my work as I hope other structural relationships will come to light, but all replies are much appreciated,
elas
 
  • #34
Alexander
well, because the difference between psi-function of various isotopes of the same element is in 5-th digit only, make sure that your semi - empirical formula can fetch that far.
 
  • #35
566
6
Originally posted by elas

I seek to explain why element 92 is almost 300 times the mass of element 1 but only three times the size,...
Elas; there are several considerations that need to be addressed in trying to develope an empirical formula for atomic size, which make it almost prohibitive.

Ist, element 92, for example, has 92 positive charges accelerating each electron, which, you would think, should actually shrink the orbits. However, there is something else that you forgot to take into account.
There is something called "shielding".

This, in effect, is due to successive 'layers' of electron orbitals at various distances from the nucleus. The innermost electrons actually 'shield' successive outer electrons from the full electrostatic effect of the nucleus. This effect, the combined effect(and its magnitude) is probably the hardest thing to quantify especially at higher atomic numbers.

Creator
 
  • #36
elas
I very much appreciate the advise particularly from those with professional training in Particle Physics. I have taken an amateur interest in cosmology for many years. As a follow on from this I ended up dealing with the question of the structure of fundamental particles; in the belief that the closer one reaches back to the beginning the simpler the problem should be, and the simple problems are all I can manage.
There is a very simple system for finding the radii (if they exist)of elements and isotopes, and I intend to finish finding them and then look to see if I can go any further. In this I am encouraged by the lack of firm reference on the subject matter.
Mant thanks
elas
 
  • #37
elas
I have at last found an authoritive quote-

....."However,the nuclear and atomic properties of isotopes can be different. The electronic energy levels of an atom depend upon the nuclear mass. Thus corresponding atomic levels of isotopes are slightly shifted relative to each other."
(From an ancient science encyclopedia in our ancient library)

My method reveals the amount of shift per nucleon added or removed in terms of mass and radius. If anyone is aware of such a method already in existence I would like to have the details, otherwise you are going to be bored with my amateur version in the near future.
 
  • #38
elas
Please go to "Vacuum force model in "theory Developement
 

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