Atoms

Walls

bonkey

Well,. when you start talking about something as large as an atom (which can be viewed using electron-tunnelling microscopes) then its not really theory

Not being snippy, but if you could ask a more "directed" question, I might be able to offer an answer without regurgitating half a book to cover all odds.

Are you asking about sub-atomic particles (the current "elementary" particles), or something else?

Also, bear in mind that there is no "current theory" on any of these things. Once we get down to the scale of these elementary particles, we start dealing in Quantum Mechanics, or String Theory, or any one of a variety of possible models.

This is where the confusion is....no fully-fledged model exists once we get to a small enough scale. Is this what you're asking for - the state of play at this level?

jc

scipio_major

I think that currently it is that:

Electrons are fundamental particles,

Neutrons are made of electrons and quarks.

Protons are made of more quarks than electrons.

The Nucleus is still in the centre with the elctrons is a field around it.

While it has been theories that quarks are not fundamental particles I don't think anyone has yet been able to "split the quark"

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Scipio_major

stereo_steve

Hey Clain, I'm a chemistry student and I don't know much about the physics side of it eg the quarks etc. But I do know about the Electron configuration! Unlike what they teach you in secondary physics, there are no set paths for the electrons to orbit. There are only areas in which there is a high degree of probabilty of finding an electron.

The electron configuration of for example of AL is:

1S2, 2S2, 2P6, 3S2, 3P1

The above represents five different areas in which there are electron levels. The S ones are spherical, and the p ones are dumbbell shaped. So 1s2 is the first orbital and contains two electrons. You know what, I'm getting confused writing this! My text book has about 2 chapters on the subject! Hopefully I answered some of your questions!

bonkey

Originally posted by Clain
When being taught elementary physics in school I was given the neutron-proton-electron model. The electron was held to have a steady orbit around the proton (I think?). As I understand it now, no steady orbit can be said to exist - particle/wave dichotomy seems to occur. And Protons and Neutrons? Uncertain. And wasn't there something about quarks? Smaller again than atoms?

OK. I need to get hold of some reference material at home to answer this fully, but basically, a set of "elementary" particles has been identified, and I believe that the existence of most of these have been verified through scientific research. This group includes quarks, electrons (yes, it is an elementary particle!), neutrinos, and so on.

As for the "orbits" theory you get taigh in secondary (Bohrs?).......thats a gross simplification of what happens, but one which is sufficient for most practical work, as long as you dont descend below the atomic scale. In other words, it explains non-quantum behaviour neatly, but clearly falls apart once you get to the quantum scale (which is where wave vs particle comes in).

I'll see what I can find you.

jc

seamus

The last thing I heard/read about it was that they thought quarks may be elementary particles, but they can't isolate any to attempt to destroy one. The discovery of quarks came about in that huge atomic accelerator yokie. Neutrons, etc are accelerated and smashed against eachother at close to the speed of light and the collision is projected onto a (very)special type of photographic sheet. Streaks can be seen shooting away from the explosion, which they believe are left by quarks, but currently they haven't been able to 'catch' a quark, only see its path as it shoots away from the collision. That's pretty simplified version, and it may be way out of date, but.........

scipio_major

WHAT are the fundamental constituents of matter? Once scientists thought atoms were indivisible, but during the early decades of the 20th century they discovered that atoms are made of protons, neutrons and electrons. Electrons really do seem to be "fundamental", but in the 1960s physicists began to realise that protons and neutrons are made up of smaller particles, which they came to call quarks.

Particle physicists now recognise two families of basic building blocks - the quarks and the leptons (which include electrons). There seem to be six members of each family, that is, six kinds of quark and six kinds of lepton. Only two types of quark, called up and down, are necessary to build the proton and the neutron, but four other types seem to be needed to build more exotic, short-lived particles found in cosmic rays and in experiments that study high- energy particle collisions.

Quarks are quite different from leptons. The main difference is that the quarks are subject to a fundamental force called the strong force, which leptons do not feel. The strong force binds quarks together within more complex particles such as the proton, where they form part of a teeming world of surprising complexity.

I really am feel peachy about the NewScientist archive. The above is from an article called "World of Quarks". I don't think there has been any advances since when it was published (10 Jul 1993). And I think it answers the components of the atom question.

As for structure it is pretty much accepted that the electrons are in a kind of cloud (metaphors escape me) surrounding the nucleus where everything else is all squashed up. The Cloud has a number of "shells" where the highest energy levels of electrons are farthest away for the nucleus. I think I'll stop there until I actually get my physics degree.

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Scipio_major

scipio_major

You know after reading the above I say your friend believes in the particle nature of life. I was always under the impression that light was a wave (energy moving without matter). Am I outdated in thinking this, have they found particles of light?

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Scipio_major

DeVore

Scipio_major, I dont know where you are getting your information from but you are very very badly wrong.

Neither neutrons nor protons are made up of electrons at all. Electrons are negatively charged and protons are positively charged for a start.

Atoms are made up of Protons and Neutrons in the nucleus, and electrons "orbiting" that nucleus. These are elementary particles. Quarks are at a lower level and are the building blocks of elementary particles.

What I cant believe is that noone here picked up on what it a fairly basic error... I mean, thats secondary school stuff...


DeV.

seamus

Originally posted by scipio_major
You know after reading the above I say your friend believes in the particle nature of life. I was always under the impression that light was a wave (energy moving without matter). Am I outdated in thinking this, have they found particles of light?

No. But current theories say that light is a combination of both wave theory and particle theory. Photons are 'packets' of light energy (I think) that travel in waves (highly simplified)

scipio_major

Neither neutrons nor protons are made up of electrons at all. Electrons are negatively charged and protons are positively charged for a start.

Atoms are made up of Protons and Neutrons in the nucleus, and electrons "orbiting" that nucleus. These are elementary particles. Quarks are at a lower level and are the building blocks of elementary particles.

Hmm I'm sorry, I had read that protons & neutrons were made of quarks and electrons. the Basis for this comes from the fact that if you split an nucleus, electrons are released. If there were no electrons there in the first place where did these newly free electrons come from?

Also I thought were we talking about fundamental particles and I know for a fact that Neutrons and Protons aren't. Which begs the question what do you think they are made of Devore?

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Scipio_major

bonkey

Originally posted by DeVore
Atoms are made up of Protons and Neutrons in the nucleus, and electrons "orbiting" that nucleus. These are elementary particles. Quarks are at a lower level and are the building blocks of elementary particles.

Actually, the term "elementary particles" was initially used when science theorised that although the atom was not the smallest indivisible "piece" of matter, that electrons, neutrons and protons were.

Since then, they have discovered that while electrons do appear to be indivisible, neutrons and protons are not. Thus, they are no longer classified as "elementary" particles, except in secondary school where the quantum level is pretty much completely ignored.

jc

bonkey

Originally posted by scipio_major
Hmm I'm sorry, I had read that protons & neutrons were made of quarks and electrons. the Basis for this comes from the fact that if you split an nucleus, electrons are released. If there were no electrons there in the first place where did these newly free electrons come from?

You do not split nuclei, you split atoms. This is where the electrons come from - they are typically released as an atom is split into two "lighter" atoms, where the sum of the electrons in each of the new particles is less than the quantity in the original.

You can also split protons and neutrons. What gets released here are elementary particles (typically top n bottom quarks) and photons, not electrons.

jc

bonkey

Originally posted by scipio_major
While it has been theories that quarks are not fundamental particles I don't think anyone has yet been able to "split the quark"

Actually, I dont think it has been theorised in any serious way. Quantum Mechanics holds quarks as elementary particles, while the various flavours of string theory hold that the elementary particles such as quarks are the "manifestation" of multi-dimensional strings (or p-branes) which are the most basic structures.

In short, there is no promising theory which requires that quarks have sub-components, and their non-divisibility is actually pretty much required for any of our current theories.

jc

DeVore

Also I thought were we talking about fundamental particles and I know for a fact that Neutrons and Protons aren't. Which begs the question what do you think they are made of Devore?

What bonkey said.

Electrons Protons and Neutrons all "operate" at the same fundamental "level".

Protons and Neutons make up the nucleus of an atom (and the vast majority of its weight). they are in turn made up of quarks and photons.

<opinion>
There are several different kinds of quarks which my memory fails me on now but I think they are Top Bottom Up Down Left Right and Weird but I'm very very unsure of those. They may have found more since I left Maths too.
</opinion>

I think we should be very careful about playing armchair scientists here. Do not put forward things you think are fact simply because you think you remember it from a Discovery Channel program once. I'd prefer if people were honest about what they are certain about and whats speculation.

oh yes, and all through secondary school... all that chemistry and particle physics they taught you. Lies. Its all Lies.

DeV.

bonkey

Originally posted by DeVore

<opinion>
There are several different kinds of quarks which my memory fails me on now but I think they are Top Bottom Up Down Left Right and Weird but I'm very very unsure of those. They may have found more since I left Maths too.
</opinion>

<correction>
There are six types of quarks, given the odd names of up, down, strange, charm, bottom, and top, in order of increasing mass.
</correction>

I also have to correct something I just posted...

So-called "beta-decay" does occur in nuclear fission, where a neutron appears to split into a proton and a highly energetic electron. I need to go check up on what is actually happening, because I dont believe that there is actually an electron "inside" the neutron , but I could be mistaken....

doh!

jc

scipio_major

Right first of yes I was talking about Beta decay when I said that about neutron releasing electrons on break up. I didn't think there was any doubt on it but what do I know? A retorical question before anyone answers.

As for fundamental particles I refer you to the ealier post from NewScientist, the be all and end all of all knowledge. That there are two types of fundamental particles: quarks and leptons (of which electrons are a type).

Seeing as I have no real way to check this against another source, I'd be interested in knowing what are.

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Scipio_major

Bob the Unlucky Octopus

If I remember right, there are 6 types of quarks: Up, Down, Happy, Sad, Strange, and Normal.

And DeVore's right...there have been 1 or 2 howlers in this thread, some of it is basic GCSE level Physics comprehension (or lack thereof :P)

Occy

Typedef

It's probably a mute point but if an election exists as both a particle and a wave should it really be called an elementary particle?

Bob the Unlucky Octopus

It isn't a 'moot' point (:P) because electrons are basically particles that occasionally behave like waves, just as photons occasionally behave like particles. So they are both waves AND particles if you like...quantum physics is about probability of states rather than strictly defined state. Heisenberg made it impossible for us to identify a defined state of an electron's position/path/orbit anyhow.

Occy

Typedef

Oh right :P. Interesting, a photon has no mass but is a particle, but being massless can accelorate to light speed, what I have difficulty with the concept of a massless thing of substance(particle), it seems to defy all the logical constraints that one would associate with the word 'particle'.

Still I would seriously doubt that quarks are the smallest 'elemental particles' in the universe as atoms were once thought to be the 'smallest' things or 'elementary particles' in the universe. Also the uncertainty principal negates every really knowing anything for sure, it's a good job I'm an ambigious person by nature, I think.

scipio_major

Two things first: What is this logic thing people keep going on about? And why can't it ecept that there are waves which sometimes act like particles by bouncing or stuff. (If this sounds like a turn around it is because I have actually did some reading up in the mean time).

Second, while it is possible that the quark is not a fundamental particle and can be split into something else. Which can in turn be split into to something else, which can be split into.... , which can be.. Ad infinitum. There will come a point there our own technology and imagination will be unable to go any further. The question is have we already reached that point?

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Scipio_major

Bob the Unlucky Octopus

par·ti·cle Pronunciation Key (pärt-kl)
n.

1) A very small piece or part; a tiny portion or speck.

Physics.

a) A body whose spatial extent and internal motion and structure, if any, are irrelevant in a specific problem.

b) An elementary particle.

c) A subatomic particle.


Now where in that, or any other definition of a particle did you get the idea that it had to have mass by virtue of 'logical constraint' Typedef? Perhaps it's the idea of mass-less energy that bothers you. Space-time has no mass, yet energy is involved as a constant in Kreblau's equation. The concept is abstract, but it is fundamental to the nature of how our universe is structured. If light had mass, it wouldn't be light. As it behaves like a particle on occasion, it is made up of a particle structure, which is and has to be mass-less. It also occupies a special point in space-time, as a photon hasn't aged a microsecond since the creation of the universe. Or if you wanted to be picky, the energy occupying that photon hasn't aged, nor would the photon.

posted by scipio major:
That there are two types of fundamental particles: quarks and leptons (of which electrons are a type).

I haven't read the article, but I was under the impression that the types of elementary particles were classified under the nomenclature of leptons and hadrons not quarks. Quarks aren't fundamental particles, they're subatomic ones, at least I thought they were.

Occy

scipio_major

I haven't read the article, but I was under the impression that the types of elementary particles were classified under the nomenclature of leptons and hadrons not quarks. Quarks aren't fundamental particles, they're subatomic ones, at least I thought they were.

This may be another case of the long understood "Lies to Children" concept. That is to say because only a qualified phyisicist really understands what goes on, people explaining anything are forced to simplify it until their audience can understand the basics of what's going on. Often by removing the technical terms (eg Hadrons) and replacing it with a term (Quark) which the sudience are comfortable. The temtation to just head over to the Physics dept right now and sort this out is quite high. Though do I really want to miss by Maths Lecture to find out?

Decisions decisions. *ponders*

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Scipio_major

Raptor

Slightly off topic, but the makeup of light seems to contradict itself. You say that it has no mass. But if it is massless, shouldnt gravity have no effect on it at all. As far as I know, light IS deflected by gravity, which seems to prove it HAS mass. But if it has mass, how does it travel at the speed of light, as its mass would increase to infinity as it approaches this velocity?!?!? I'm in fifth year atm, so there could these "facts" may not be accurate, so claification would be very helpful.

bonkey

Raptor - light is not structly affected by gravity. Rather, gravity appears to effect the actual curvature of spacetime through which light is travelling.

Think of the famous rubber sheet analogies. Draw a grid on a flat sheet. Now distort the sheet by adding masses to it. The "straight" lines now appear curved. Effectively, the curvature of light is done on the same principle.

Also, I would point out that the concept of gravity being linked to *mass* is not necessarily correct. Remember that most of these "facts" which we work off are derived from Newtonian physics, or at best from Special Relativity. While both of these models are sufficiently accurate for most purposes, they are not fully correct nor are they complete.

Therefore, the first thing we must do when discussing areas like this is double-check what model our so-called facts are coming from.

Take the particle/wave duality of matter. How can a particle be a wave? Well, it cant. Not really. But sort-of. When we talk about a particle at a quantum level, we cannot clearly define it. Its existence is "smeared" across a set of probabilities...which is mathematically represented as a wave. If we look at string theory we see that there are other types of "waves" used to define matter. So, at a certain scale, the concept of a particle no longer makes sense - it is invalid. However, when we go to a slightly larger scale, and change our model, we see that it makes more sense to talk about particles.

So - how about the indivisibility of the current elementary particles. How can we be sure that these particles are indivisible? We cant. Its that simple. However, we can say with a high degree of certainty that our best current models indicate that there isnt another layer between where we currently are, and Planck Length - the smallest distance at which the concept of matter makes any sense. The fact that we have now models which "work" all the way to Planck Length and below is where the strength of this lies. The models may be wrong, but previous "smallest" claims never had such models, which is why we are not so surprised in hindsight that they were superceded.

I would also like to also clarify the use of the word "particle" slightly. Its usage does not mean "having mass" or "being made of matter". Rather, its name implies that the stuff in question can be looked at in terms of discrete "packets", sometimes called quanta.

So, at the moment, we mostly have field-theory (gravity etc), particle-theory and wave-theory, with all three overlapping depending on which model you use, and the scale you work at.

We talk about electromagnetic fields, which are composed of electrons, which can be expressed as particles or waves. So when we discuss electromagnetism, are we discussing field, particle or wave theory? This is a nonsensical question - the answer is actually "we are discussing whichever theory is relevant to the discussion at hand".

So - stop trying to bend you brains on whether something is a particle or a wave. It depends on what model you are looking at it under

jc

Ciaran

As far as I understand it, the smallest 'particles' (rather not get into the particle/wave thing) that are known about are:

Quarks of which there are 12 types (up, down, charm, strange, top, bottom and all the anti-particles equivalents). They come in three 'colours' (green, red, and blue). They can combine to form larger particles in any combination which leaves the reulting particle 'white' i.e. green + red + blue or red + anti-red etc.

Leptons of which there are 6, I think (electrons, taus, some other one that I can't remember and their anti particle buddies).

Neutrinos of which there are 6 (one corresponding to each lepton).

Photons (light and also seemingly involved in 'communication' between charged particles to cause electro-magnetic forces)

There are also particles (Ws, I think) which do the communication job for the strong nuclear force. I don't know if they are made up of the above or not. These have, as far as I know, been detected.

Finally there is postulated to be a graviton which does a similar job for gravity. This is a quantum idea which, I think, is inconsistant with General Relativity.


Someone mentioned beta (can't get Greek symbols to work) radiation. This happens at the level of quarks; an up quark decays to a down quark and an electron (it may be a down to an up, I don't remember exactly). What this means for a quark being indivisible, I'm not sure but I don't really see how an 'elementary particle' can decay to something else.