Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: that mad man on 17/09/2007 21:31:57

Title: Where is the proton
Post by: that mad man on 17/09/2007 21:31:57

Hi, hope you can help!

As I understand it the neutron is at the centre of the atom, so where is the proton placed?

Does the proton have momentum or is it stationary?

Bee

Title: Where is the proton
Post by: Soul Surfer on 17/09/2007 22:38:42

Nothing in this universe is truly stationary.  The uncertainty principle (position error times momentum error equals Planck's constant) means that everything is jiggling about a bit even if it has no extra energy.  The lighter the thing is the greater is its uncertainty in position and momentum,  Both protons and neutrons form the nucleus of the atom which is quite small because its mass is the greater part of the mass of the atom and so the uncertainty in its location and momentum is quite small but the lighter electrons have a much greater uncertainty of position and momentum. Also most of them have to have some extra angular momentum to ensure that they are all a bit different from the other electrons in that atom  (this is due to the Pauli Exclusion principle) so they jiggle around a lot more and this mean that the overall "size" of atoms is determined by how far the electrons can get away from the nucleus and still be held by it which is much larger than the nucleus.  If electrons had a mass equal to protons, atoms would be about the size of the nucleus and everything would be almost as dense a neutron stars!

Title: Where is the proton
Post by: that mad man on 17/09/2007 23:18:15

Thanks Soul Surfer for that as you have explained it well in a way that I can understand.

What I am trying to understand is although it all "jiggles" about does the proton have momentum around the neutron or do they interact or revolve around each other. They cant be side by side for instance.

Not sure of the size of a proton vs a neutron?

Bee

Title: Where is the proton
Post by: Soul Surfer on 17/09/2007 23:49:11

Protons and neutrons are now known to be composite particles each of which consists of three quarks bound strongly together a bit like they were joined with slightly elastic strings. The quarks themselves are moving about violently because there is more energy associated with their movement than the masses of the quarks themselves.  the joining fore between protons and neutrons is the strong force associated with these quarks and is a bit like Velcro ie sticky at very short ranges  (around 10^-13cm) and that is around the size of the nucleus and the individual nucleons.

The actual process of bonding in complex nuclei is not very well understood and not easily accessible for investigation although more interest is being generated by heavy ion colliders.  It is a bit like electrons in that complex nuclei  seem to form shells and have particularly stable and unstable configurations but they are not the same as the electrons in the outer parts of the atom.  Complex nuclei can also be considered to be a bit like liquid drops and do exist in excited states as well as the basic ground states.  The energy levels however are many times greater than those of the electron shells being in the MeV range (gamma rays)  whereas electrons are a few Ev (light) in the outer shells and X-rays around 100Kev for the innermost electrons of large atoms.

Title: Where is the proton
Post by: that mad man on 18/09/2007 00:16:31

Thanks again, bonding was the word I was after!  [8D]

So, would it be safe for me to say that we just don't know at the moment only that they form the nucleus, bond, have energy and "jiggle" about?

I thought wrong, that if the neutron was stationary in the centre then the proton must be somewhere else close to the neutron and may be moving around it forming a shell.

Can you help with another related question.  [:)]

Electrons - move about the nucleus + but why do they jump in state rather than in a linear transition?

Bee

Title: Where is the proton
Post by: DoctorBeaver on 18/09/2007 21:01:49

Quote from: that mad man on 18/09/2007 00:16:31

Electrons - move about the nucleus + but why do they jump in state rather than in a linear transition?

Bee

Sic transit gloria quantum  [;)]

Title: Where is the proton
Post by: Soul Surfer on 18/09/2007 23:32:34

Back around the turn of the twentieth century the classical physicists studying physics and electromagnetic processes worked out that if the electrons behaved in a classical linear way the electromagnetic radiation from warm matter should get greater and greater without limit as the frequency got higher this would cause the universe to be unstable and collapse in on itself due to the powerful electromagnetic attraction between electrons and protons.  Quantum theory solved this problem and it has been proved extemely accurately by many observations even though it is very wierd.  So you could say that if the electons did not have fixed energy levels that they jumped between the universe as we know it just wouldn't exist.

Title: Where is the proton
Post by: lightarrow on 19/09/2007 12:10:20

Or, as simplicistic explanation, we can say electrons in an atom are actually standing waves and so they "vibrate" in discrete ways, every way is an "orbital" with a specific energy.

Title: Where is the proton
Post by: DoctorBeaver on 19/09/2007 15:48:06

Quote from: lightarrow on 19/09/2007 12:10:20

Or, as simplicistic explanation, we can say electrons in an atom are actually standing waves and so they "vibrate" in discrete ways, every way is an "orbital" with a specific energy.

That's simplistic?  [???] [:-\]

Title: Where is the proton
Post by: that mad man on 19/09/2007 19:29:08

Thanks all.

I can understand about the way in which an electron moves around the core and it has been describe as like a mist inside the atom. I am a layman and can also understand a bit about the uncertainty principal, planc length and quantum packets.

What I have found hard to understand or find out about was the nature of the question posed. Most of what I have seen or read seemed to imply that the neutron was at the centre and the proton shown to one side and that both make up the core.

Now I know that they in fact bond with each other.

To be honest, with electrons I didn't really mean in a straight linear fashion but one that increases or decreases in state rather than jumps.

Bee

Title: Where is the proton
Post by: Soul Surfer on 20/09/2007 21:59:33

You are probably taking the illustrations of atomic structure that you find in most textbooks far to literally. It is not only electrons that have a degree of uncertainty in their position and velocity.  All atomic particles are a bit fuzzy and to talk about the precise positions of protons and neutrons in an atomic nucleus does not make any sense.  (anyway they each consist of three tiny particles behaving like they were connected together with strings and moving at speeds very close to the velocity of light) Also the drawings cannot be to any scale because if you include the size of the electron cloud in an image that fits neatly on an A4 page the nucleus is so small that it would not be visible.