Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 04/06/2015 21:50:02
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Atul sharma asked the Naked Scientists:
Why is it not that electrons bind together by the nuclear force and reside inside it, and protons move along around it?
What do you think?
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Because "electron" is the name we give the the negatively charged particles on the outside of an atom, and "proton" is the name we give to the positively charged particles in the middle.
And the words "positive" and "negative" are equally arbitrary.
There is no "why" in physics. We name the constituent bits of the universe, and construct mathematical models of "how" it works.
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In the old days you had Electrons inside the nucleus but QM does not allow it except in Neutron stars
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anti matter?
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Why is it not that electrons bind together by the nuclear force and reside inside it, and protons move along around it?
Because the nucleus has much more mass than electrons do. Objects with greater mass orbit the center of mass of the system further out than other objects of less mass. If the mass of one object is significantly greater than the other then the object then that object will remain almost at rest close to one point. This happens for the same reasons that the planets orbit the Sun which remains at rest at the center of our solar system.
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Why is it not that electrons bind together by the nuclear force and reside inside it, and protons move along around it?
Because the nucleus has much more mass than electrons do. Objects with greater mass orbit the center of mass of the system further out than other objects of less mass. If the mass of one object is significantly greater than the other then the object then that object will remain almost at rest close to one point. This happens for the same reasons that the planets orbit the Sun which remains at rest at the center of our solar system.
so the electron does circling the proton in a hydrogen atom?
is the electron orbital 2 d or 3 d?
Thanks! Good morning!
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so the electron does circling the proton in a hydrogen atom?
is the electron orbital 2 d or 3 d?
Thanks! Good morning!
You are, as always, confusing the "classical" Bohr model with the quantum model. Orbitals are 3 dimensional probability density maps. The electron does not "circle" the proton, which is why we use the word "orbital" and not "orbit".
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please explain the details.
what is propability density map? do we have a pdm for solar system?
we are talking science right?
1 proton and 1 electron, how the hydrogen atom is formed?
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anti matter?
As jccc says, you could make an atom out of an anti-proton (which has a negative charge), and an anti-electron (which has a positive charge; it is also called a positron).
In this case, the positive charge would circle around the negative center.
As PmbPhy says, the anti-proton is much more massive than the positron (by a factor of almost 2000 times), so you could imagine the negative nucleus as staying stationary*, and the positive orbital surrounds it.
* In reality, there is nothing really stationary in relativity or quantum theory.
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so the electron does circling the proton in a hydrogen atom?
Nope. I never used the term "circle." I said "orbit." I.e. that's why there are electron orbitals instead of proton orbitals.
You really need to start paying attention to what you read.
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what's difference between circle and orbit?
is hydrogen atom's electron orbital 2 d or 3 d?
what's the mechanism?
Thanks!
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what's difference between circle and orbit?
Pick up a text on quantum mechanics and learn the difference. I've told you the difference so many times now that I'm sick to death of it and it's clear that you'll never learn it until you stop being a spoiled brat and do the adult thing and learn physics the right way, like the rest of us who do understand it. The other way, by asking questions and paying attention to the answers, doesn't work for you as you've proved to us many times.
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There is no "why" in physics.
Nice! [:)]
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There is no "why" in physics.
Nice! [:)]
really? [B)]
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I had a series of discussions with an old, retired electron, sometimes ago, and he used to say that he always see a proton orbiting round him, when he worked in the hydrogen-atom firm.
[;D]
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lightarrow
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really? [B)]
There are different views on this. Quite often science can't supply answers to "why" questions. However many scientists think that the goal of science is to provide answers to such questions. As Mendel Sachs explains in his text Concepts of Modern Physics: The Haifa Lectures on page 4
Though some scientists believe that the descriptive level of science is all that there is to know, that is, they believe that scientists
should only ask ‘what’ questions, I believe that the explanatory level that follows the descriptive level is the actual goal of science — the answers to the ‘why’ questions.
Experience tells me that more often than not science has only provided what questions. However there is a place for why questions in science too such as Why is the sky blue? and Why does the Earth have a magnetic field? etc. Those questions have answers.
And of course I've explained all of this to you before and like everything else, you forgot about it.
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I had a series of discussions with an old, retired electron, sometimes ago, and he used to say that he always see a proton orbiting round him, when he worked in the hydrogen-atom firm.
[;D]
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lightarrow
which orbital was he in charge?
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I guess there are two colloquial interpretations of "why". One is indeed asking for an elucidation of mechanism, and "why is the sky blue" is less clumsy than "what mechanism can you propose and test that would make the atmosphere appear blue when illuminated by the sun and viewed from below?" but that's quite different from a "philosophical" why, which seeks an ulterior motive for things being as they are.
The third interpretation is known as the "jccc question". You take an absurd proposition and ask why it isn't true. This form of "why" seems particularly common on science forum boards, and the answer is often "because the implied question is absurd". The implication is "why is the sky blue when according to my calculations it should be red" - in other words, the answer lies in the realms of psychology: delusions of grandeur or omniscience, etc.
As always in physics, if the world doesn't meet your expectations, your expectations are wrong.
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I had a series of discussions with an old, retired electron, sometimes ago, and he used to say that he always see a proton orbiting round him, when he worked in the hydrogen-atom firm.
[;D]
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lightarrow
which orbital was he in charge?
He didn't remember the exact name because he kept changing to higher levels, but he remembered that the last one had n = 137 and that he were in a "Rydberg" atom:
http://en.wikipedia.org/wiki/Rydberg_atom
The similarity of the effective potential ‘seen’ by the outer electron to the hydrogen potential is a defining characteristic of Rydberg states and explains why the electron wavefunctions approximate to classical orbits in the limit of the correspondence principle.[3] In other words, the electron's orbit resembles the orbit of planets inside a solar system, much like the obsolete but visually useful Bohr and Rutherford models of the atom used to show.
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lightarrow
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Google "f orbital shapes" to see just how wrong the "planetary orbit" model is.
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Google "f orbital shapes" to see just how wrong the "planetary orbit" model is.
Are you answering me? If you do, I have to inform you that you haven't read carefully what I've written and the wiki link.
I repeat: in Rydberg atoms, orbitals can really be almost classical orbits.
Electrons behave almost classically there. Have you ever heard of "classical limit"?
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lightarrow
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what's difference between circle and orbit?
My understanding is that the only real difference is that most natural orbits are not quite circular. However, I think the question you may have meant to ask was "what's difference between circle and orbital?"
The answer to that is in #6 and probably in several other places.
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In the old days you had Electrons inside the nucleus but QM does not allow it except in Neutron stars
What do you mean by "the old days"?
Some orbitals don't have a zero probability density of being inside the nucleus. Is that what you mean? In situations like neutron stars the electrons combine with the protons to form neutrons. However a neutron is not a proton with an electron inside of it.
what's difference between circle and orbit?
is hydrogen atom's electron orbital 2 d or 3 d?
what's the mechanism?
Thanks!
God damn it, jccc! I fail to understand why you can't do what we all do and that's to look it up in Google if we don't know the answer or its not in one of my textbooks on physics.
From Wolfram - A circle is a geometric entity, i.e. a circle is the set of points in a plane that are equidistant from a given point O. An orbit i
From Wikipedia - An orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System.
re - is hydrogen atom's electron orbital 2 d or 3 d?
Here we go yet again explaining things you should already know but don't because you're too damn lazy to read and have to be spoon fed like an infant. Again, your confusing orbital with orbit. They are entirely different concepts. A hydrogen atom has many orbitals associated with it. The "2" or "3" corresponds to the energy level of that electron while the "d" represents l, the angular momentum quantum number corresponding to l = 2. See http://en.wikipedia.org/wiki/Atomic_orbital
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What do you mean by "the old days"?
Wasn't there a time when the atom was thought (by some?) to be a lump of positive matter with negative inclusions, like currents in a pudding?
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What do you mean by "the old days"?
Wasn't there a time when the atom was thought (by some?) to be a lump of positive matter with negative inclusions, like currents in a pudding?
Yup. It was called the plum pudding model, hypothesized by J. J. Thomson in 1904.
http://en.wikipedia.org/wiki/Plum_pudding_model
In particular I was asking what he means by the old days since there were various steps to a complete theory of quantum mechanics.
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Wasn't the electron a bit of a family thing with the Thompsons? If I remember rightly JJ identified the electron as a particle, and his son discovered its wave nature.
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Wasn't the electron a bit of a family thing with the Thompsons? If I remember rightly JJ identified the electron as a particle, and his son discovered its wave nature.
Yep. Your memory is spot on (although you spelled his last name wrong which made it difficult for me to do a search). Good for you my friend! :) His son's name is George Paget Thomson
http://en.wikipedia.org/wiki/George_Paget_Thomson
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Bohr produced a physical model of the hydrogen atom which involved simple algebraic equations. QM defined the hydrogen atom using very complex math. Is the universe a simple place or a more complex place? If we add the Einsteinian energy to the Bohr model we find that the neutrino is the amount of energy for the electron to reach a speed of 0.9186C as it reaches the proton radius. This can only happen if we compress the hydrogen atom to the neutron. That is a simple explanation. QM may be a mathematical solution but does it really tell us how things work? In effect it is another model which tells us some things but does not tell us everything. It fails to provide us with an understanding of gravity and dark energy. Therefore it is only a particular theory which is useful in describing the workings of particles and sub-particles as we bash them up. Since it is hard to understand by the average person, its value in explaining the universe is quite limited.
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the neutrino is the amount of energy...
I'm afraid I don't understand this.
Do you mean the rest mass of the neutrino (https://en.wikipedia.org/wiki/Neutrino#Mass)(there are 3 kinds of neutrino known)? This has proven very difficult to measure, but is thought to be somewhere around 0.1eV (and the different kinds of neutrino may differ by a few orders of magnitude).
energy for the electron to reach a speed of 0.9186C as it reaches the proton radius
- If you imagine an electron as a negative point charge, being attracted from an initially stationary position towards the proton in the centre of a hydrogen atom, it could well reach relativistic speeds.
- Or if you imagine an electron as a negative point charge, being attracted towards the proton in the centre of a hydrogen atom, it would need to reach relativistic speeds to stay in a circular orbit.
But an electron is not a point charge, nor does it take on a circular or elliptical orbit around the nucleus. The electron fills a 3-dimensional orbital around the nucleus of an atom.
The QM description of an atom describes the orientation of atomic bonds in 3-dimensional space. It also explains the shape of the periodic table (https://en.wikipedia.org/wiki/Electron_configuration#Periodic_table). This cannot be matched by a "Solar System" model of the atom.
So QM is more complex, but it also gives better predictions. At this point in time, the Solar System model of the atom is mostly useful as an introduction to the structure of the atom, but it should never be presented as a definitive model!
If (like me), you can't solve Schroedinger's equation (https://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation), then we must accept the answers from those who have used powerful computers to model the structure of complex atoms in detail. (And it does take relativistic effects into account.)
It fails to provide us with an understanding of gravity and dark energy.
At this point in time, there is no proven explanation for Dark Matter, let alone integrating gravity with the subatomic world. So that is no reason to prefer one theory over another.
Instead, you should choose a theory to use based on the accuracy you require from its predictions, and your ability to manipulate the theory to produce answers of the required accuracy.
But why "reinvent the wheel"? You could just look up a textbook prepared by someone else which already has tested answers based on physical measurements and/or theoretical predictions.
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Bohr produced a physical model of the hydrogen atom which involved simple algebraic equations. QM defined the hydrogen atom using very complex math.
You're confusing the terms model and define. QM models the hydrogen atom using partial differential equations.
Is the universe a simple place or a more complex place? If we add the Einsteinian energy to the Bohr model we find that the neutrino is the amount of energy for the electron to reach a speed of 0.9186C as it reaches the proton radius.
What do you mean by "Einsteinian energy" and what does it have to do with the hydrogen atom. The hydrogen atom is modeled using non-relativistic QM. And by the way, the neutrino has nothing to do with the hydrogen atom. And the term "speed" doesn't apply to electrons in an atom. The concepts of speed and velocity are foreign to QM.
This can only happen if we compress the hydrogen atom to the neutron.
I can't imagine where you got this notion from? What are you claiming happens? I.e. what is the "this" that can only happen as you suggest?
QM may be a mathematical solution but does it really tell us how things work?
That's incorrect. QM can tell you everything that can be known about how things work. It's not merely a mathematical solution. Layman seem to invariably confuse the math of physics with physical reality. As is well-known to all physicists, math is the language of physics. That means that we describe everything that can and does happen in nature with math, at least in principle.
It fails to provide us with an understanding of gravity and dark energy. Therefore it is only a particular theory which is useful in describing the workings of particles and sub-particles as we bash them up.
That's not a failure of quantum mechanics. It's merely out of its domain of applicability.
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But an electron is not a point charge, ...
Physicists assume that the electron is a point charge. There is every reason to assume that it is and no reason to assume that it isn't. See:
https://en.wikipedia.org/wiki/Electron
The electron has no known substructure.[1][74] and it is assumed to be a point particle with a point charge and no spatial extent.
See also: http://www.fnal.gov/pub/today/archive/archive_2013/today13-02-15_NutshellReadMore.html
The quarks, leptons and bosons of the Standard Model are point-like particles.
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Let’s start with the easiest point-like particle we know, the electron... To begin with, since it has zero size, you can never actually see the electron itself.
...
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In the first instance, the electron should not be treated as a particle but as a wave that is orbiting the nucleus.
The electron does not spiral into the nucleus because it is a wave.
One experiment that I have performed on numerous occasions is observing standing waves on a string. Attach a one metre string to a mass and feed this over a pulley attached to a bench so the mass dangles over the bench. The other end of the string is attached to an oscillator which is connected to a signal generator. The string is now horizontal and quite taut. The frequency is varied till the string vibrates in its fundamental mode (the simplest standing wave). This could refer to an electron in the ground state. Now if the frequency is increased then the standing wave disappears and eventually a new standing wave is formed at a particular frequency called the second harmonic. This can represent the electron in the first excited state, above the ground state. This experiment is beautiful because now the students can be informed that the electron cannot exist between the energy levels, as no standing wave formed. Also, the exact frequency was required to move from the first harmonic to the second, I.e. the need for the correct photon energy between energy levels.
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In the first instance, the electron should not be treated as a particle but as a wave that is orbiting the nucleus.
The electron does not spiral into the nucleus because it is a wave.
One experiment that I have performed on numerous occasions is observing standing waves on a string. Attach a one metre string to a mass and feed this over a pulley attached to a bench so the mass dangles over the bench. The other end of the string is attached to an oscillator which is connected to a signal generator. The string is now horizontal and quite taut. The frequency is varied till the string vibrates in its fundamental mode (the simplest standing wave). This could refer to an electron in the ground state. Now if the frequency is increased then the standing wave disappears and eventually a new standing wave is formed at a particular frequency called the second harmonic. This can represent the electron in the first excited state, above the ground state. This experiment is beautiful because now the students can be informed that the electron cannot exist between the energy levels, as no standing wave formed. Also, the exact frequency was required to move from the first harmonic to the second, I.e. the need for the correct photon energy between energy levels.
Very neat explanation. This kind of demonstration goes a long way towards fostering understanding where mathematics may frustrate it.
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In the first instance, the electron should not be treated as a particle but as a wave that is orbiting the nucleus.
You're suggesting that people visualize the atom using the outdated Bohr model. That's a bad idea. People should think in terms of quantum mechanics (QM). In QM one obtains a wave function whose physical meaning is that the modulus of that function, when its normalized, is the probability density. As such in one of the energy states there is a finite probability of finding the electron inside the nucleus.
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what's difference between circle and orbit?
I doubt that you'll understand this or remember it for more than a few seconds but I thought I'd show it to you so that you'd have no excuses for saying that I never explained this to you, even though I'd explained it countless times.
This article describes the difference between Bohr orbits and atomic orbitals. See the first two figures in the following article:
http://mightylib.mit.edu/Course%20Materials/22.01/Fall%202001/why%20nuclei%20decay.pdf