Arrangement of Neutrons and Protons in the Lithium Nucleus?

[NoAstronomer]

My daughter has been given a middle school project to create a model of a Lithium-6 atom. I thought it would be cool to show the nucleus with a set of six balls representing the protons and neutrons.

However I can't find a decent reference for how we should arrange them. The sources that seem most promising are research papers I don't have access to.

Any ideas? or is this something that scientists haven't actually figured out yet?

The one source we did find that had a diagram was not what I considered reliable.

[Kaptain K]

In truth, just about any arrangement would do. The nucleons are not rigidly stuck together. Just alternate the two so the positively charged protons are separated as much as possible by neutrons.

[grant hutchison]

And in fact, the protons and neutrons are constantly converting back and forth by the exchange of virtual pions, so any "arrangement" changes constantly.

Grant Hutchison

[parejkoj]

One can map out the arrangement of charge within a nucleus through scattering experiments. I don't know whether this has been done for Li-6, though. We did some basic computation to that effect in a quantum mechanics course, I believe. It's not easy.

I think a group at MIT did a computation to that effect. I'll see if I can find the link.

[antoniseb]

I had been involved with some studies on this for Gold and Mercury atoms.
Basically, for Li6, the above statements are on the money. There is no fixed position. Please, also, do not think of a Proton or Neutron as having a well defined surface. They are made of Quarks.

[korjik]

Like what everyone else said

There is no real fixed position, or even a fixed identity for the individual protons and neutrons. Quantum Mechanics gets funny that way. If you just try your best to keep the protons away from one another, you will keep the physicists happy.

[Jeff Root]

I think it would be a good idea to squish the balls together a bit,
perhaps by flattening or cutting off some material from the parts
of the balls that will be in contact with each other.

-- Jeff, in Minneapolis

[parejkoj]

Ok, found what I remembered, but it wasn't what I remembered. The physics department at the University of Florida hosts a chart of the Fermi-surfaces for a bunch of things. Not exactly what you're looking for, but kinda neat anyway.

[JohnD]

For a really fancy model, use pingpong balls and put a bicolour LED in each, that change colour in unison. The location of the blue (say) neutrons and red (for instance) protons will then change constantly. Let it twist on a fine suspending thread and no one will be able to tell which is where!

John

[trinitree88]

My daughter has been given a middle school project to create a model of a Lithium-6 atom. I thought it would be cool to show the nucleus with a set of six balls representing the protons and neutrons.

However I can't find a decent reference for how we should arrange them. The sources that seem most promising are research papers I don't have access to.

Any ideas? or is this something that scientists haven't actually figured out yet?

The one source we did find that had a diagram was not what I considered reliable.

NoAstro... ...and remember that the nucleus in proper scale to size of its' electron cloud, is roughly the size of a baseball sitting in Yankee Stadium/Yankee Stadium...it's pretty tiny, which is how things slip through if they're neutral, and unaffected by electrons or protons...like fast neutrons and neutrinos. Just tell people the entire school grounds that she's in represents the electron cloud.
In the forties Yukawa suggested the exchange of virtual mesons mediated the strong force, and his numbers predicted pretty much the mass of the pion (although he was mistakenly awarded grace when the muon was discovered..a lonely Nobel error). No nucleus with more than a single proton can exist without stabilizing neutrons, which themselves are unstable without protons nearby.
The best thing about lithium is that it shows up in cherry red bursts from fireworks on the Fourth....of July, but you might con an eccentric millionaire into tinting the sun...see:http://www.bautforum.com/questions-a...alter-sun.html pete.

[IsaacKuo]

Hmm...no one in this thread seems to have put much thought into specifically how six balls of two colors could actually be clustered together in the model. One way is to cluster them together like the six faces of a cube. This minimizes the overall diameter of the structure.

If you do this, then there's no way to make the balls "alternate" between colors. The best you can do is a sort of tennis-ball arrangement with three protons in a "C" shape cupped against the three neutrons in another "C" shape. This is what happens if you place two protons in opposite locations, and the third has no choice but to neighbor both of the previous protons.

But this gets me thinking...there's no need to minimize the overall diameter of the structure. The three neutrons could be placed in a triangular formation, and the three protons stuck to them to form the corners of a larger triangle.

Or the neutrons and protons could be placed in a hexagonal ring formation, alternating protons and neutrons.

[kzb]

<<Hmm...no one in this thread seems to have put much thought into specifically how six balls of two colors could actually be clustered together in the model. >>

You also need to take into account that neutrons are "deeper" in the nucleus than the protons, and both have a separate shell structures with paired particles in each shell. Or in this case there will be 2 full shells and two shells with one nucleon each.

But then it's school, I think this is getting into it in too much detail

[antoniseb]

...Or the neutrons and protons could be placed in a hexagonal ring formation, alternating protons and neutrons.

That won't be it. The binding force of the nucleons is far stronger than the charge repulsion. Also, try to keep in mind that even though the protons and neutrons have dimensions, they can and do pass through each other. kzb's comment about the shell model is very mainstream and tested on larger nuclei.

[Jeff Root]

even though the protons and neutrons have dimensions, they can
and do pass through each other.

That's why I suggested squishing them together some.

-- Jeff, in Minneapolis

[Celestial Mechanic]

A representation that I would use would be this:

Two protons and two neutrons put together to form a tetrahedron. This is because the lowest energy state for the nuclear potential is a 1s_1/2 level. Think of this as an alpha particle "core" for the nucleus.

Put the remaining proton on one side a small distance from the core and the neutron also at a small distance directly opposite the proton. These two particles are in a 1p_1/2 state which is the next available energy level. I believe that they should be in the same p orbital to maximize their overlap and thus their mutual attraction.

As with all such models, they only imperfectly represent what is going on, but I think this is sufficient for the intended purpose. Anyone more knowledgable about this please feel free to correct me.

[Michael Noonan]

I had been involved with some studies on this for Gold and Mercury atoms.
Basically, for Li6, the above statements are on the money. There is no fixed position. Please, also, do not think of a Proton or Neutron as having a well defined surface. They are made of Quarks.

By meaning not well defined does that mean rough? If the surface could be imaged would there be a comparison made to the known roughness of the cosmic background radiation perhaps?

Or is there a specific point of weakness at one or both ends that might be known perhaps?

The questions I ask are based on ideas that are not of mainstream origin and I appreciate BAUT has done all it can to assist me push my idea as far as I can, cheers

[antoniseb]

By meaning not well defined does that mean rough? If the surface could be imaged would there be a comparison made to the known roughness of the cosmic background radiation perhaps?

By not well defined, I mean not solid. If you are looking for a macroscopic analogy, and willing to take one that isn't perfect, what is the 'surface' of a globular cluster? We can talk about the globular as having a mass and a brightness, and other properties, so it can be thought of as 'an object', but as to the surface, there are increasing probabilities of all the stars in the cluster being within a certain radius as that radius increases, but there is a decreasing chance of a star being within a cubic light year as you move away from the center.



Image linked from "A Review of the Universe".

As I said, the analogy isn't perfect, forces and dynamics that affect the motions of three bound and charged quarks is not an inverse square law applied to a many bodied problem, but I think that the globular cluster is a good example to explain what I mean by a surface being not well defined.

[Michael Noonan]

By not well defined, I mean not solid. If you are looking for a macroscopic analogy, and willing to take one that isn't perfect, what is the 'surface' of a globular cluster?
(snip)

Thank you antoniseb
I guess it wouldn't be easy for a forum to accommodate a member who applies what could only be described as unorthodox thinking. The analogy works very well for me and especially the picture of a globular cluster approach.

Cheers

[Jeff Root]

If you are looking for a macroscopic analogy, and willing to take one
that isn't perfect...

Huh??? What do you mean by "an analogy that isn't perfect"???

I, too, think the analogy with a globular cluster is outstanding,
especially with the photo of Omega Centauri. The individual
stars are a bit too fuzzy (emulating their parent cluster?), but
the number of stars and the symmetry are spectacular!

-- Jeff, in Minneapolis

[antoniseb]

Huh??? What do mean by "an analogy that isn't perfect"?

The difficulties with analogies is that they are useful for some aspects of the comparison, but that too often, people will feel that by extension that some other aspects of the analogy must also work. For example: people talk about the expanding universe being like the surface of an expanding balloon. There have been new members here in the past that have assumed, by extension, that eventually that balloon will reach its elastic limit and pop.

Similarly, in the globular cluster case, if six globular clusters were put together like in a Lithium nucleus, they would not retain their identities, but would irreversibly mix...

But the analogy does work for showing the indefinite surface of particle made of probabilistic component particles.

[manmeetvirdi]

Make a placard write "A Li-6 atom" on it and point it towards an empty space.
you are done!!