Atomic Q&A

There is a web site of free educational videos at: www.khanacademy.org

I found this video on "Introduction to the atom"
https://www.khanacademy.org/science/chemistry/introduction-to-the-atom/v/introduction-to-the-atom

As part of this video, there is a Q&A section where people have written a number of fundamental questions. I decided I would try to answer some of these and here are my answers.

"What's inside the protons and neutrons? "

According to conventional theory, a proton and a neutron are made up of 3 quarks. The up quarks (U) contain a +2/3 charge and the down quark (D) contains a -1/3 charge. A proton is UUD (2/3 + 2/3 - 1/3 = 1) and a neutron is DDU (-1/3 + -1/3 + 2/3 = 0).

This appears to be strongly motivated by the fact that we have found 3 point particles in a proton. It is "assumed" that there must be 3 point particles in an neutron (although there is little to no scientific evidence of this) and the only way to make this work out is to have the partially charged quarks.

Of course, no one has ever found any direct evidence of a partially charged quark particle. This isn't due to lack of trying or that it should be fundamentally impossible to find. All the experiments have failed. Science has never ever seen a partially charged particle.

This whole mess could be easily resolved if we didn't think that the neutron had to be made up of 3 particles. If you take the more reasonable assumption that a neutron is made out of only 2 particles, then you could make a neutron out of just a whole charge positron and an electron. A prroton could be nothing more than 2 positrons and 1 electron. Is this not easier than thinking we have 1/3 charged fractional particles that we have never ever seen? That's my take on it IMHO.

"Why do we see and feel things like a wall or a table as a solid object when they are really mostly free space? "

Yes, how is it something that is 99.999% free space be "solid"?

This seems totally wrong. If objects really were that much free space, then you'd think that things would just pass by each other.

The answers provided by others are telling you that it is the "negative" electrons around the atoms which are pushing with the electrostatic force. Well, if that were the case, then because all atoms are surrounded by this same negative repulsive field, then how can any atoms stick together at all? They should all just repell each other by that same logic (or illogic). So that can't be the answer.

The other problem is that if it is really only the electrostatic force keeping objects apart, then with enough force, you absolutely can overcome that force and you should be able to "meld" objects together with enough force. So, I should be able to get 2 biliard balls to meld or literallly pass through each other if 99.9999% of space is empty. But that doesn't happen, the billiard balls will splinter and never stick together.

In my opinion, this view that matter is 99.9999% empty is 100% wrong - as wrong as thinking the Earth is flat or at the center of the universe. We think matter is mostly empty based on an experiment done by Rutherford who fired particles at gold foil. I think firing particles at a gold foil is a pretty blunt instrument for finding the size of a atomic nucleus. But the results Rutherford got could be explained by a tiny positively charged nucleus. Everyone loved the idea because it made the atom look like a tiny solar system. Nobody bothered to question the experiment or conclusion. Just because the experiment confirmed that it could be a tiny nucleus, it did not prove that it "was" a tiny nucleus. It could still be the nucleus is big but reflects particles using non-electrostatic forces.

So I question this whole notion that space is 99.999% empty. Find me an experiment that really proves this - look on the internet, you won't find one.

The reason why we see a "solid" wall is because it really is "solid". The atoms are filled with particles that take up the physical space and there is no vacuum at all. The reason why objects do not pass through each other is not the electrostatic force, but simply the principle that 2 objects cannot occupy the same piece of space at the same time. Whether you are a billiard ball or an electron, the physics of real particles works the same at all scales. They have "hard, ponderable surfaces". That is what you feel.

"I understand how quarks comprise the constituents of atoms, and how atoms comprise molecules, and so on; however, I do not understand how we know atoms are real. Can anyone help?"

So, you want to see an atom? Well here it is:

http://franklinhu.com/siatom.jpg

If you follow that link, you will see a recent picture of a silicon atom crystal. You can see that each ot the atoms look like lego blocks. This is using a technique called Scanning Tunneling Microscopy. If you want to read up on it, you can view the paper that this picture came from:

http://franklinhu.com/Herz%20PRB%2068%2045301%202003.pdf

This is far, far better than Rutherford-like scattering experiments where you fire bullets into a black box and try to figure out what is in the box. This is more like a "photograph" of an atom. What we see is not the 99.999% empty space atoms. What we see are space filling lego bricks which have a definite shape that occupies the entire width of the atom.

"What makes a proton have a positive charge? What makes an electron have a negative charge? Why does a neutron have a 'neutral' charge? "

The answers that quarks have charge does not answer the question which is what makes something have charge. There has to be some difference between a proton (or positron) and electron that make them so that opposites attract and similar repel.

Conventional science has no answer to this question. If any honest scientist were asked this question, the honest answer would be "I don't know". This seems to be a pretty basic thing for us to "not know" considering it makes up the bulk of forces that act on atoms.

So what alternatives are out there. The only physical explanation for why one object should attract another object across a distance is described in this paper:

http://franklinhu.com/AHLeahy.pdf

This paper written way back in 1884 shows that pulsing spheres in a compressible medium create an attractive force if they are pulsing out of phase and a repulsive force if they are pulsing in phase. The force has been experimentally been shown to act exactly like the electrostatic force between opposite charges which a 1/r^2 distance relation.

So if a proton and electron were merely pulsing spheres which are out of phase, then the "thing" that makes a proton have a positive charge is this "pulsing" and a specific frequency and phase. The "thing" that gives an electron a "negative" charge is the same pulsing, but just at opposite phases. The proton and electron each send out waves and it is the interaction of these waves that we observe as 'charge'.

You won't find this in any textbook, but this is the only physical explanation I can find which can explain what is the thing that gives protons and electron "charge".

I think that a neutron is nothing more than a proton (or more accurately -a positron ) which is paired wth an electron. When the proton pulses out, the electron pulses in and vice versa. Because of this, the pair doesn't get bigger or smaller, it stays the same size and it doesn't produce waves like a bare proton or electron would. Since there is no wave generated, there is no charge. This is why a neutron has a 'netural' charge.

"How does an electron stay in orbit when it's going that fast? Doesn't that mean that the nucleus has gravity, coz i thought that only planets and stars and stuff have gravity. "

When Rutherford came up with the 'planetary' model of the atom, it was literally a mini solar system with the tiny nucleus in the middle with the electrons orbiting the nucleus like the Earth orbiting the sun. There was no gravity, instead there was the electrostatic attraction of the positively charged nucleus (the sun) to the negatively charged electrons (Earth).

A beautiful picture - huh? Everyone just fell in love with this picture because it agreed with an existing bias that an atom should act like the solar system which we already knew about. After all, we just tossed the Earth centered universe in favor of the Copernican and Newtonian vision of orbits and gravity, so it was an easy sell.

While beautiful and easy to understand - it could not be more wrong. You ask the basic question - "how can all these electrons possibly stay in orbit". I think the answer is that "they can't" and that there is something seriously wrong about our picture of the atom.

First, everything we understand about electrons tells us that an electron cannot orbit around the nucleus like the Earth around the Sun. The electrostatic force laws tell us that the electron has to be radiating away energy as it orbits around the nucleus and that the orbit must quickly decay. Energy is not radiated away when the Earth is in orbit using gravity, so it can remain stable. People have tried and tried to work out how the electron might not be radiating and have generally all failed.

The other problems are why don't all these electrons run into each other. They came up with the Pauli exclusion principle which just says that they don't, but that isn't a reason. In a Uranium atom with 92 electrons flying about in all different shells with orbital shapes like balloon animals tied together - it is beyond belief that these electrons can stay in orbit without instantly colliding into a huge mess.

Quantum mechanics tries to side step this problem by saying that the electron is actually found in a "cloud" described only by probability functions. So we can ignore this whole problem by saying the electron isn't orbiting - it's "clouding" or something and the normal laws of physics need not apply.

Doing something like this is what is known as adding an "Ad hoc" hypothesis. In science and philosophy, ad hoc means the addition of extraneous hypotheses to a theory to save it from being falsified. There is absolutely nothing to justify it except to save a theory from being falsified. Saying an electron is a "probalistic cloud" does not excuse it from radiating if it is in any kind of motion around the nucleus.

So if the electron isn't orbiting, then what is it doing? I think we need to go back 100 years and take a serious look at failed atomic models like JJ Thompson's plum pudding model and see where the train left the track for atomic theory.

We fell so in love with the Rutherford planetary model, that we didn't see it created more problems than it solved. The electrons can't be orbiting or taking any kind of position outside of the nucleus and an atom is not a solar system with gravity.

"If protons are positive, how are they able to be so close to each other and so densely packed in the nucleus? Wouldn't they repel each other due to their like charges? Thanks "

Of course, the protons would repel each other. They repel each other with some extremely high amount of force - something in the 100's or even 1000 lbs of force. The sole reason why we think the protons are packed together like this is the Rutherford experiment, where Rutherford had to "assume" that positively charged alpha particles were reflected back "only" due to the positive electrostatic force of the nucleus. The only way it could be done was by "concentrating" all the positive charge into a microscopic speck in the middle of the atom. Otherwise, there wouldn't be enough electrostatic force to reflect back the positively charged alpha particle. If you didn't notice, that was a lot of unfounded assumptions being made there.

The standard answer to this question is that it is the "strong force" that holds together the protons. The problem with this answer is that we might as well say "green fairy dust" holds the protons together because we have just about as much scientific evidence for the green fairy dust as we have for the strong force.

The explanation for how the strong force works goes something like this. The strong force is an "exchange force" where particles passing back and forth called pions cause an attractive short range force. If you believe that, then I think I got a bridge for you to buy. Just how on earth is passing a particle back in forth create an attractive force? Now they have found particles like pions which have approximately the right mass that they calculate for this exchange force - however, there is no evidence that these particles actually participate in this exchange force. Just because you find something that weighs about as much as a duck doesn't mean you found a duck. You probably just found a rock that weighs the same thing as a duck. Yet this is the type of evidence used to prop up the "strong" force. I'm thinking green fariy dust is a more likely explanation.

So, how can we explain how the protons can be so close to each other? Well, I think you should reconsider the question of "why" you think protons are do densely packed in the nucleus. Can you show me any independent scientific experiments which are not directly realated to the assumptions made by the Rutherford experiment that independently confirm the size of the nucleus as this dense object? We should have 2 or 3 completely different experiments that directly confirm the location of the charges within an atom. But it seems we only have Rutherford type scattering experiments which all make the same assumptions and agree with each other. However, that experiment could be fatally flawed based upon the unfounded asumptions it starts out with.

So it could be that the answer to this question is that the protons are not densely packed in the nucleus. It could be that the protons and electrons are arranged in some kind of checkboard pattern that completely neutralizes the electrostatic forces and utterly eliminates the need for a mysterious and completely made up "strong" force.

"So if Atoms are made of quarks, what are quarks made of, well the chain be infinite does something have to be made of something else? "

They'll tell you that "quarks" are fundamental particles and they aren't made of anything else. That's about the same as saying that quarks are made out of little green fairy dust. No one has ever been able to isolate one of these particles and it hasn't been for lack of trying - they just can't find any. So these quarks might as well be fairy dust since there's about the same amount of scientific evidence supporting either idea.

If you are gonig to have an full explanation of atoms, then I don't think you need to go down the infinite rabbit hole of explaing every sub-particle. But you do need to get down to a particle that you know exists. For example, if I had an atomic theory that somehow ultimately relied on the existence of apples, then my atomic theory has a proper foundation since I know apples exist in the world. I may not know how apples come into existence or what is inside an apple or how it works, but that's OK because we know apples exist and their properties are well known. On the other hand, nobody's ever observed a quark or come up with any direct credible evidence for their existence (not indirect or implied), so building your atomic model on quarks is building a castle in the air.

So what particles could we call upon to create a firm foundation for an atomic model? I would say that the only candidates are the positron and electron. We know these particles definitely exist becuse we clearly see them in our experiments, we use them everyday in applications like medicine and electronics. Their existence is beyond doubt. Plus, every particle that decays, decays only into positrons and electrons eventually. There is no other mass particle that anything decays into. So this makes it a good candidate for the particles that make up everything.

Atoms could still be made out of quarks, but in order for it to not be a castle in the air, even quarks would have to fundamentally made out of positrons and electrons to have a proper theoretical foundation. However, this is not what current theory states.

"Why do we conclude that 99% of everything is free space, why don't the electrons' orbitals overlap each other? "

Based upon the shapes given for the various s, p d, f orbitals, I would think that the barbell and balloons tied together shapes would most certainly overlap the spherical s orbitals. In fact, based upon the fact that the electron has only a probability of being in an area means that every electron could potentially be in any spot around the atom. So how is the Pauli exclusion principle supposed to work if any electron can be practically anywhere and all of these orbitals overlap and chaos should ensue? It flatly doesn't make any sense how the electron would know how to maintain its position around the nucleus.

As many other people have noted, it doesn't make sense to conclude that 99% of everything is free space either.

These are good solid questions which do not have good solid answers to them. Because of this, I think we need to look back at the initial assumptions that lead us to this mysterious path of 99% nothingness and electrons which magically maintain their overlapped orbitals .If only 1% of everything was free space and electrons didn't orbit at all, this would be easier to understand.

"If opposite charges attract, why doesn't the electron just stick to the nucleus? Why does it keep 'orbiting' around it?"

Actually, nothing should keep it orbiting around. A big problem with the 'planetary' model of the atom is that the electron must radiate energy as it goes around the nucleus. It must lose energy and must spin down into the nucleus.

Your question is about why doesn't the electron just stick to the nucleus after it has spun in. Well, that seems like a pretty obvious thing for an electron to do. It would be just like two magnets sticking to each other. I like to think that this is exactly what happens. Electrons do not orbit the nucleus. In the case of hydrogen, we would have an electron that is just sitting on the proton. No fancy orbits required.

However, if you talk with people about a proton and electron coming together, they treat it like it would produce some sort of catastrophe - they can't even begin to imagine something like this happening. I think part of the reason why they can't imagine what happens is because they treat the proton and electron as some theoretical mathematical point with no surface or radius. It's infinitely small. When you start to think there are things which are infinitely small, you get into Zeno's paradox whereby an arrow should never reach it's destination because it must travel half way to the target, then it must travel half again and again and again. It would take an infinite number of such steps to reach the target, so, the arrow should never reach the target.

So these same people have a hard time wrapping their brains around a proton and electron which are approaching each other at infinitely small distances. So they can't ever meet each other - forever falling into each other. Or, they think they will blink out of existence or be unstable or some other unmentioned catastrophe.

Earnshaws's theorem which states that any set of charges cannot be stable is also cited as a reason why the electron cannot sit on a proton. However, once again, this is based on the unfounedd "assumption" that you can treat protons and electrons as theoretical point charges (which they certainly are not).

Instead of making this crazy assumption that protons and electrons are point charges, why not make the intuitive assumption that the laws of physics work at all scales from billiard balls down to electrons where all particles have ponderable physical surfaces with distinct a distinct radius. Then, it is quite possible for an electron to rest on a proton. But too many people love making the "point charge" assumptions which forces us to keep electron orbiting around eventhough they can't be.