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/sci/ - Science & Math

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4193046 No.4193046 [Reply] [Original]

Hey /sci/ so how come negatively charged electrons don't spiral and crash with the positively charged nucleus? I'm pretty sure it has something to do with the quantum theory. But not sure.

>> No.4193054

wavelength of the electron is too wide to fit into the nucleus.

>> No.4193053

If you need to ask this question then I don't think you're capable of understanding.
It's just magic, okay.

>> No.4193058

Magic.

>> No.4193061

It'd be like trying to put your dick into an electrical outlet.

>> No.4193065

>>4193046
The neutrons cock block.

>> No.4193075

>>4193046
In the Bohr model, it's simply an assumption that electrons travel in circles. Another assumption is that electrons on those circles don't radiate, therefore don't lose energy, therefore don't spiral around. ("It's magic" kind of fits this.)

If you do the basic quantum mechanical calculation, you'll see that the probability of the electron being in the center is 0 (which isn't surprising, 0 is just a single point after all). This however assumes a point-sized nucleus, but seeing that this model already has probabilities instead of defined trajectories that's not really your question's concern anymore.

>> No.4193078

>>4193046
Its some bs about how a nucleus radiates energy

>> No.4193080

>>4193075
I think his question was more directed towards WHY the probability is zero for being at the nucleus.

>> No.4193088

>>4193080 at the nucleus
At the center, i.e. the point <span class="math">0[/spoiler]. I have no idea how to calculate the thing with a finite sized nucleus that can possibly react with the electron. Proton/electron collision might be a good start, but I'm not sure about that.
Anyway, a single point is a Lebesgue zero subset of <span class="math">\mathbb R^n[/spoiler], therefore all integrals over that set vanish.

>> No.4193091

>>4193088
The nucleus is not a point.

>> No.4193093

>>4193075
And now I'm wondering why there's no apparent implications of the nucleus not being a point. There's some small probability (/ distribution) of the electron being arbitrarily close to a proton, right? So electrons should show some amount of colliding with protons, right?

>> No.4193094

So what would happen if, at say CERN or something, they forced an electron and a proton to collide?

>> No.4193101

There are other forces involved (the nuclear forces) which repel electrons from the nucleus. Atoms are not analogues to solar systems where there is only one force involved in the motion of orbiting bodies. Overcoming the nuclear forces requires electrons to fly at the nuclei with an enormous amount of speed; its why fusion requires such immense temperatures and pressures.

>> No.4193105

>>4193094
neutron + neutrino

>> No.4193107

>>4193094
A gazillion of different outcomes are possible from that. What you have here is a <span class="math">4\to n[/spoiler] process, i.e. 4 particles (<span class="math">e^-[/spoiler] and <span class="math">uud[/spoiler]) smash into each other, producing <span class="math">n[/spoiler] new particles.
I've never dealt with bound states in that respect, i.e. "proton electron collision in a stable atom", so I can't really help you with that. I don't even know whether the question is relevant somewhere.

>> No.4193106

>>4193094
strangely, see >>4192443

>> No.4193108 [DELETED] 

except they can if they have several nuclear partners, although they really don't 'crash' into the nucleus (see electron capture)

it's primarily energy. atoms in the 'real world' aren't perfect little things in the middle of nowhere. they are constantly struck with photons, thus the electrons are always absorbing and remitting energy, creating a situation that is nearly impossible for one to be in the same energy state more than a couple milliseconds. there is also consistent coulomb interaction with nearby atoms/molecules, which apply force on the electrons in countless directions.

>> No.4193116

>>4193101
now explain weak and strong nuclear force please

in layman's terms

>> No.4193119

>>4193116
>nuclear force
>repel
pick one

>> No.4193121 [DELETED] 

>>4193101
>There are other forces involved (the nuclear forces) which repel electrons from the nucleus.
electrons do not have color charge, what the fuck are you smoking?

>> No.4193129 [DELETED] 

>>4193119
there are a few models which hypothesize anticolor repulsion

>> No.4193178

There is a probability of it being in the nucleus at any time.
Using delta p delta x > h/2pi
for x the size of the nucleus, p is such that v > c.
So it cannot remain there.

>> No.4193315
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4193315

The electron is dispersed in a type of cloud surrounding the nucleus and it can be modeled as a wave-function whose value at some point from the nucleus corresponds to some type of probability density used to model a dispersion relation.

Even with a firm understanding of the mathematical underpinnings of quantum mechanics the ideas often appear esoteric and subtle.

>> No.4193321

>>4193178

now that's interesting; I didn't know electrons could spent part of their time within the nucleus.

>> No.4193522 [DELETED] 

>>4193321
You must nut have taken much physics then...

>> No.4193528

it's either the weak or strong force/interaction.

too lazy to look up which it is exactly.

>> No.4193534

>>4193046

QUANTUM mechanics, not classical mechanics:
http://en.wikipedia.org/wiki/Energy_level

>> No.4193542

>>4193119
Nuclear force becomes strongly repulsive at <span class="math">very[/spoiler] small distances.

>>4193106
eh? Doesn't that assume they are travelling in the same plane immediately before the collision?

>> No.4193548

>>4193315
>>4193321

This is why you shouldn't ask /sci/ for help/information.

>> No.4193566

>>4193542
What makes you think that the strong force becomes repulsive at small distances? QCD doesn't predict any repulsion.

>> No.4193569

>>4193566
...just to begin

"The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers, but rapidly decreases to insignificance at distances beyond about 2.5 fm. At very short distances less than 0.7 fm, it becomes repulsive, and is responsible for the physical size of nuclei, since the nucleons can come no closer than the force allows."
-http://en.wikipedia.org/wiki/Nuclear_force

>inb4 wiki unreliable source

>> No.4193582

>>4193569
that has absolutely nothing to do with pion exchange or QCD.

that is the pauli exclusion principle in effect, just like we observe with electrons. quarks have antisymmetric wave functions.

>> No.4193591

"Because of its wave nature, the electron wants to spread itself over as large a volume possible, so that its wavelength will be large and its kinetic energy will be small. Its almost as if the electron is being repelled by the nucleus."

Taken from The Quantum World by Kenneth Ford.

Now shut up faggots about magic. Its not that hard to explain in simple terms.

>> No.4193593

>>4193591
that's so ridiculously pseudoscientific i almost fell off my chair laughing.

>> No.4193606

>>4193593

>simplified explanation
>pseudoscientific

This shit is why everybody hates science

>> No.4193612

>>4193606
it's not simplified at all.

>Because of its wave nature
an electron is not a 'wave'.

>the electron wants
electrons do not 'want' to do anything. they are pushed around by photons.

>to spread itself over as large a volume possible
an electron is a 0-dimensional point. a point cannot spread itself.

>so that its wavelength will be large
the wavelength of an electron's matter wave is proportional to its rest mass. 511keV is not large, it is very, very small.

>and its kinetic energy will be small.
what? the electron, if it is trying to do anything, is gaining KE to escape the wrath of its nuclear partner.

>Its almost as if the electron is being repelled by the nucleus.
it's not being fucking repelled at all, there's positive charge inside the nucleus. it has a proton as a nuclear partner. they attract each other by exchanging virtual photons.

>> No.4193613

>>4193582
No. While it is not really clear how the repulsive portion of the potential arises from first principles QCD, it is definitely not just Pauli blocking.

Lattice calculations DO show a repulsive portion in the potential.

>> No.4193624

>>4193613
please show me experimental evidence suggesting this. i'd love to know.

>> No.4193625

>>4193624
start with this
www-het.ph.tsukuba.ac.jp/~saoki/NForce.pdf

>> No.4193629

>>4193624
what do you mean with experimental evidence?
The whole of nuclear physics tells you that the potential at short range is repulsive. The mechanism behind this potential isn't fully understood as of now.

>> No.4193641

>>4193625
that only demonstrates that a repulsive core is present. this was known. the pauli exclusion principle is very applicable to nucleon-nucleon interaction, and i quite frankly do not understand why we need this 'repulsive' element of the nuclear force. we see the same effect in EM potentials.

>>4193629
there's plenty of successful hartree-fock calculations without this repulsive element.

>> No.4193646 [DELETED] 

>>4193612

your statement about the electron's wavelength being proportional to its rest mass is abjectly false.

According to the DeBroglie relation, any particle's wavelength is related to its momentum, by:

p = hbar*k

where k is the wavenumber of the particle, and p is the momentum.

Thus for a particle with an extremely high momentum, its wavelength (proportional to 1/k) will be very, very short. It can be arbitrarily far in magnitude from the particle's rest mass.

>> No.4193653

>>4193612

your statement about the electron's wavelength being proportional to its rest mass is abjectly false.

According to the DeBroglie relation, any particle's wavelength is related to its momentum, by:

p = hbar*k

where k is the wavenumber of the particle, and p is the momentum.

Thus for a particle with an extremely high momentum, its wavelength (proportional to 1/k) will be very, very short. It can be arbitrarily far in magnitude from the wavelength corresponding to the particle's rest mass.

>> No.4193658

>>4193612

Simplify is reduce the complexity of. What is easier, say an electron "wants" to have an negative charge or explain in detail why the electron is bound by various law to have said charge?


>an electron is not a 'wave'.

The author refer to the wave behavior of the electron in this specific case

>electrons do not 'want' to do anything. they are pushed around by photons.

Already explained

>an electron is a 0-dimensional point. a point cannot spread itself.
But it has a wavelength that can, in fact, spread itself. And in the end what really "spreads" is its possibility of being in in a determined point.

>the wavelength of an electron's matter wave is proportional to its rest mass. 511keV is not large, it is very, very small.

We are talking about sub-atomic standards. An atoms diameter is gigantic by them.

>what? the electron, if it is trying to do anything, is gaining KE to escape the wrath of its nuclear partner.

The larger the KE, the smaller the wavelength. At the nucleus it has infinite KE. See anything wrong in that?

>it's not being fucking repelled at all, there's positive charge inside the nucleus. it has a proton as a nuclear partner. they attract each other by exchanging virtual photons.

If that were the only force acting on the electrons, they would eventually spiral into the nucleus. The electrons do not follow a model of "Nucleus Sun and Electron planets" in the classical view for this reason

>> No.4193666

>>4193658
I'm not the OP, but:
>The larger the KE, the smaller the wavelength. At the nucleus it has infinite KE. See anything wrong in that?
If so, why do we see electrons depart from atoms when they absorb a photon of sufficient energy?

>> No.4193680

>>4193666

Anyways, I think is related to conservation of momentum, but I don't really know. Sorry.