Talk:Neutron

I'm not sure the description of particles in a nucleus as resonances between protons and neutrons by exchange of pions is up to date. I remember it was one of the first strong interaction models that appear, but that was before quarks and QCD. Is that description still valid in a quark context?

Yep. QCD provides a little more detail to the picture, of course, but you still get triples of up-downs which correspond to proton-neutrons, and since these are colorless and gluons very sticky you tend to get quark-antiquark pairs connecting them, and these are pions.

Here is the thing, My name is Jessi and I am in 8th grade we just started learning about Atoms,Protons,Neutrons,Elcrtrons,exc, and i am just haveing some trouble understanding it all. It is so comfusing

Importance in chemistry

I did a Google search and I got a page saying that neutrons are not important in chemistry. Please complete this sentence:

Although neutrons are not important in chemistry, they are important in... 66.245.84.123 00:53, 28 Sep 2004 (UTC) (No, my IP address is not a part of this sentence.)

Ummm... It's not actually true, although many people who should know better do say that it is. The number of neutrons in its nucleus doesn't make much difference to the chemical behavior of an atom, but it does make some. If you drank enough heavy water to make it replace somewhere between a third and two-thirds of your body water (nobody has tried it), your hair would fall out and any fast-growing cancers would go into remission, owing to the slowing down of some very critical chemical processes in your body. And much chemical research uses radioactive tracers. And depending what you mean by important in chemistry, there's the little detail that the only stable nucleus without any neutrons is hydrogen! So without neutrons, chemistry would be a little on the boring side, if indeed there were any chemists to do it. Andrewa 01:40, 26 Oct 2004 (UTC)

It is mainly important for hydrogen where the speed of the reaction changes by about a factor of 6 under most circumstances where hydrogen is important. Otherwise, it isn't so important... none the less most living things do show significant preference for certain isotopes Pdbailey 04:09, 23 Nov 2004 (UTC)

how many neutrons are in helium?

Depends on the isotope. Helium-3 and helium-4 have one and two neutrons respectively and are the only stable isotopes of helium. Helium-6 and helium-8 (4 and 6 neutrons) are beta decayers with half-lives under a second. -- Xerxes 20:35, 2005 Jan 22 (UTC)

Half-life of free neutrons

I've noticed that there seems to be a very wide range of values given for the half-life of free neutrons. A quick Google search showed up values ranging from around ten minutes to as much as 17 minutes. Even Wikipedea's two entries on the neutron and the free neutron currently give values of 886s and "about ten minutes" respectively.

I have found a reference which gives a measurement with a range of error: http://prola.aps.org/abstract/PRD/v5/i7/p1628_1

The value they give is 10.61 ± 0.16 min (about 636.6 +/- 9.6 seconds).

I've not edited any entries to reflect this as I have not found another reference confirming this value and the error range. Perhaps someone will be able to confirm the figures.

I assume that the wide range in published values is a reflection of how tricky it is to make the measurement. It would be interesting to hear if this is the case.

Indeed these conflicting half-lives can certainly lead one into dubious waters. This simply comes down to the instrumentation used by laboratories independent to each other. One lab might use a gas chamber detector while another might use a scintillation detector with less dead time. I understand the consensus among many nuclear and particle physicists is that the half-life lies somewhere between 10.2 and 10.6 minutes. — oo64eva (AJ) ^{(U | T | C)} @ 14:53, Apr 15, 2005 (UTC)