spin quantum number

[dhruv227]

why is the spin quantum number of electrons in an atom has a value of only + or - 1/2

[mattura]

To make everything add up! Particle physics is all just a big fiddle really...

[dhruv227]

To make everything add up! Particle physics is all just a big fiddle really...

i wasnt expecting this answer i wanted a good lengthy answer

[ichwar]

i wasnt expecting this answer i wanted a good lengthy answer

Lol, My guess is that that is the best answer you're going to get from us geeks. I don't want to discourage you, but I think that if you really want a detailed explanation, you'll have to go to a more science oriented forum.

[garrettroyce]

They must be opposites so they add up to zero, otherwise the atom would have an overall charge even if it has the same number of protons and electrons. As for the value of 1/2, it's not like 1/2 an electron's charge. It has to do with the magnetic field generated by the spinning electron. A moving charge generates a magnetic field normal to it's movement, so opposite spins generate opposite electric fields. From what I understand, the value 1/2 means that the electron has 1/2 of the absolute magnetic field strength.

http://hyperphysics.phy-astr.gsu.edu/Hbase/spin.html

[mattura]

I did only particle physics at a-level several years ago, so I don't remember things that well, but I still maintain that it's all made up and fiddled to work! (along the line of "oh, we've measured a strange charge here, lets say that these other particles therefore must have half of the opposite charge to add up to a stable neutral particle...)

If you really wanted more in depth answers, you could look it up - you can usually start with google and wikipedia and follow a few links...

Lol @ ichwar!

[doctor15]

I agree that all of quantum physics is a fiddle. The human brain is poorly fitted out for imagining what goes on at this level. Physicists and mathematicians observe the behaviour of smashed up bits of matter, then try to come up with a formula which would explain what they see. Because they are not Gods, we end up with something which always looks suspect and doesn't answer all the questions. The idea of spin just fits an experimental model and giving it the value of 1/2 makes the equations balance. It's almost certainly 1) wrong and also 2) a very poor representation of what is actually going on.

Physicists are such a pain in the bum that we dug a big hole in Switzerland, buried them there, and we're not going to let them out anytime soon. I wonder why we are still paying them though?!!

[ChatIndia]

wow, we are dealing with this topic in our class nowadays on some "magnetic materials" topic. But you know, I don't pay attention in class. haha..

BTW, what's the physical significance of spin quantum number. maybe you can get some hint from there.

[dkstiler97]

why is the spin quantum number of electrons in an atom has a value of only + or - 1/2

well in your answer that has to do with the "quarks" that when they are merging to form the electron

there are 3 basic types o quarks so they have spin numbers positives and negatives and neutral .... so in that case the sum of those quarks produce the specified spin number !!!

did i cover you ?

[essellar]

I'm aware of six quarks (up, down, charm, strange, top and bottom) and their antiquark counterparts, and all are spin-1/2. That has little to do with electrons, though, since electrons are leptons, and quarks compose hadrons (protons, antiprotons, neutrons, antineutrons and mesons).

The "it's a fiddle" remark is completely correct. There is nothing magical about the ±1/2 value of spin, since it isn't an accident. If you express the angular momentum in SI units rather than as a number derived from the Planck constant (ħ), it doesn't come out to a nice round number. The fact that the value is constrained to multiples of 1/2 (all known Fermions are spin-1/2; all known bosons are integer-spin) seems to be a fundamental property of whatever the heck matter is -- and, honestly, we really have no idea what that is, which is why silly ideas like string theory keep popping up. They don't actually answer any questions. (Vibrating what? All you've done is pushed the question of "what is matter" further down the stack.) But they make the math work, and that's okay. I guess.