Neutrons

[popjinx]

Does anyone know if neutrons are actually made up of a proton and an electron fused together?

[Phi for All]

They are not. Neutrons have no electrical charge.

 

http://en.wikipedia.org/wiki/Neutron

[popjinx]

I know that. Think about it, a proton (+) plus an electron (-) would not have any charge.

[Thomas Kirby]

Disclaimer: I am not an expert.

 

However, neutrons are exactly that, a proton and an electron fused together, sometimes with some spare change. It says so in the third paragraph of Phi's wikipedia reference, where it says that a free neutron after 866 seconds decays to form a proton, an electron, and an antineutrino.

 

Beta decay is when a neutron in the nucleus of an atom releases an electron and becomes a proton. The atomic number goes up while the atomic mass goes down a tiny fraction.

[timo]

They are not. However, a neutron can decay to proton + electron + antineutrino.

[swansont]

Disclaimer: I am not an expert.

 

However' date=' neutrons are exactly that, a proton and an electron fused together, sometimes with some spare change. It says so in the third paragraph of Phi's wikipedia reference, where it says that a free neutron after 866 seconds decays to form a proton, an electron, and an antineutrino.

[/quote']

 

 

That antineutrino is key. It is not accurate to say that a neutron is made up of a proton and an electron. If you try to combine a proton with an electron you will not get a neutron unless a weak interaction occurs, changing an up quark to a down quark and emitting a neutrino. And an electron cannot be confined within a nucleus, much less a nucleon, for any appreciable length of time because of the Heisenberg Uncertainty Principle.

 

edit to add: and they do not decay after 866 seconds. That's the mean lifetime - the time to decay has a statistical distribution.

[Thomas Kirby]

I'm not in for a round of splitting hairs. So it's a proton and an electron and some small change.

[ydoaPs]

no, a neutron is made of quarks, but it decays into a proton, an electron, and an anti-neutrino.

[Thomas Kirby]

I'm going to quietly sneak away now.

[popjinx]

Thank you yourdadonapogos for giving me a correct answer. I just looked up quarks in a text and it verified your answer.

[Molotov]

I once heard neutron stars formed by gravity fusing protons and electrons together. If this isnt true then how do all the atoms in the collapsing star turn into neutrons?

[DV8 2XL]

Gravity wins if the total mass is big enough.

[ydoaPs]

then it isn't a neutron star.

[swansont]

I once heard neutron stars formed by gravity fusing protons and electrons together. If this isnt true then how do all the atoms in the collapsing star turn into neutrons?

 

By the reaaction I described above. You get a bunch of neutrinos as well.

[YT2095]

Thread moved from Chem to here, seems to be the most suitable by nature of the posts.

[danny8522003]

Im not knowledgable enough to be able to properly find flaws in a PDF file i found, it seems to explain how a neutron can be formed by combining a proton and electron.

 

The file can be viewed here.

 

Any thoughts or comments?

[DQW]

Any thoughts or comments?

Yes, it's a load of hooey !

[5614]

Any thoughts or comments?

Yes, there's a problem in the first two sentences!

 

It says:

 

"Neutrons are elementary particles that can decay into protons, electrons, and neutrinos. The inverse process, formation of neutrons from protons and electrons, has been explored in different directions."

 

Now clearly there is a problem here. It is saying that:

 

Neutrons --> Protons + Electrons + Neutrinos

 

And that the "inverse process" is:

 

Protons + Electrons --> Neutrons

 

It is not too hard to notice that this "inverse process" is not truely inverse as the neutrino has been missed out.

 

Now I ask the decay of neutrons, does it release a neutrino, an anti-neutrino or either? If either than how is it decided? If it's just one or the other then something in this thread is wrong.

[fermions]

talking about the neutron star... I heard that the electrons are actually squeezed out by the gravitational force and leaving the nucleus behind so it's something like neucleon star...

dunno if it's true or not...

[Dave]

Everything you want to know about neutron stars, and more.

[danny8522003]

When a massive star creates an iron core whose mass exceeds the Chandrasekhar limit' date=' it will collapse and create a type II supernova. The core of the collapsing star is initially composed of iron supported by electron degeneracy pressure, since the nuclear fusion of iron doesn't release energy. When the core collapses, the densities and pressures in the core overcome even the electron degeneracy pressure and the iron atoms' electrons are compressed into their nuclei where they combine with protons to form neutrons.

 

electron + proton → neutron + neutrino

 

The neutrino is emitted from the core, leaving the neutron behind.

[/quote']

 

Link.

 

Although it says there are some inaccuracies in the article so ... *shrugs*

[Meir Achuz]

"Neutrons are elementary particles that can decay into protons' date=' electrons, and neutrinos. The inverse process, formation of neutrons from protons and electrons, has been explored in different directions."[/i']

 

Now clearly there is a problem here. It is saying that:

 

Neutrons --> Protons + Electrons + Neutrinos

 

And that the "inverse process" is:

 

Protons + Electrons --> Neutrons

 

It is not too hard to notice that this "inverse process" is not truely inverse as the neutrino has been missed out.

 

Now I ask the decay of neutrons, does it release a neutrino, an anti-neutrino or either? If either than how is it decided? If it's just one or the other then something in this thread is wrong.

 

1. neutron --> proton + electron + antineutron.

This is an example of "beta decay".

 

2. One inverse process is antineutrino + proton --> neutron + positron

 

3. Another inverse process, proton --> neutron + positron + neutrino,

can only take place in some nuclei (called "proton rich").

This process cannot occur with an isolated proton because it could not conserve energy.

 

4. Another inverse process, proton + electron --> neutron + neutrino

occurs when a proton in a nucleus "captures" an inner atomic electron.

[Thomas Kirby]

Phi's answer from a while back takes a lot of explaining. The fact that a neutron has no net electrical charge means what? The proton and the electron have equal and opposite electrical charges.

 

The picture of a neutron as being a proton and electron fused together is accurate to a certain degree. A proton and an electron go in. A proton and an electron come out. The anti-neutrino is small change.

 

The fact that according to current science the neutron consists of three quarks bound together is a bit much to just throw right in there when someone asks if a neutron is an electron and a proton fused together. It's confusing enough to need an explanation. Somehow we do get a neutron when a proton and an electron are squeezed together. In a neutron star the electrons are moving at pretty high relativistic speeds by the time they are crushed into the neutrons and have a lot of energy to give up to the cause and to the surrounding space, so there's where you can get your weak interactions or your anti-neutrinos. We also know that neutrons spontaneously emit electrons during beta decay and become protons. The anti-neutrino was a pretty abstract notion for quite a while, a bit of missing mass that couldn't be located as energy or as a particle. It's still pretty edge of perception. We can't observe them nearly as directly as we can observe gamma rays, electrons, protons, or helium nuclei. It takes a lot of doing to observe quarks. Can't just haul out a handy cloud chamber or fluorescent screen.