Why only opposite spin electrons in an orbital ?

**ranadeep** · Nov8-09, 01:10 AM

Why only electrons having opposite spin should be in a orbital ? What character does spin quantum number give to electron and some more interesting things on Spin quantum number please ..

**Borek** · Nov8-09, 04:46 AM

Electrons have to differ somehow - when they are on the same orbital, they share the same characteristic (n, l & m quantum numbers) - the only way to be different is to have different spins.

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**vissarion.eu** · Nov8-09, 06:04 AM

If electron is point (at least when it is measured) then how point can have oposit spins? Point is infinity small spot which can describe only coordinates. So point is like devided into two poles or if magnificy this point to it field then have sphere (this sphere can be infinity big) divided into two poles S and N. Field deacresing with law 1/r^2.
And how magnet can attract over magnet in this configuration if to try explain atraction with spins:
___
|S|
|N|
----
___ ____
|S| |NS|
|N| -----
----

So here 3 magnets and down left magnet attracting (with S pole) two overs (N poles), how it supose to be spins of this down left magnet? In superposition to uper and right magnet? But isn't then supose amplitude to fall down? Atraction little bit decrease or here are somehow spins from inside or just only from surface electrons?

**Borek** · Nov8-09, 10:37 AM

Originally Posted by vissarion.eu

If electron is point (at least when it is measured)

It is not, its radius is somewhere in the 10^-15 m range (although different sources give values differing by about 2 orders of magnitude).

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**vissarion.eu** · Nov8-09, 12:19 PM

So then what is electron shape? Sphere? If it colapsed it can't be wave anymore, so then electron become a sphere of diameter 1/10^15 m? Or maybe cube of size a=1/10^15 m?

**Borek** · Nov8-09, 12:43 PM

I doubt electron has any 'shape'.

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**Redbelly98** · Nov8-09, 01:33 PM

Originally Posted by ranadeep

Why only electrons having opposite spin should be in a orbital ? What character does spin quantum number give to electron and some more interesting things on Spin quantum number please ..

Electron "spin" here is not the same as an object spinning around in the usual sense. However, if we are to maintain the conservation of angular momentum in the interactions we observe, it is necessary for the electron to have an intrinsic angular momentum of 1/2. This is consistent with other phenomena such as the Pauli Exclusion Principle (see Borek's comment in post #2), and the fact that an electron has a magnetic moment.

**pzona** · Nov8-09, 02:18 PM

Originally Posted by vissarion.eu

So then what is electron shape? Sphere? If it colapsed it can't be wave anymore, so then electron become a sphere of diameter 1/10^15 m? Or maybe cube of size a=1/10^15 m?

There is no "shape." An electron can't be described fully by a wave model or a particle model, that's why it has the properties of both. If you try to measure it as purely a particle, I'm pretty sure this violates the uncertainty principle.

**DrDu** · Nov9-09, 03:03 AM

In Quantum Electrodynamics (QED), the most accurate description of electrons we have right now, lectrons are point particles and don't have any shape. However, sometimes something called "classical electron radius" (see, e.g. wikipedia) is specified which would be the size a classical charge distribution of the total charge of the electron would have to have if its mass were entirely due to the energy of the electric field it produces. It is about the 10^(-15)m specified above. In QED, this is the distance below which the spontaneous production of electron-positron pairs becomes important, that is, where the single particle picture breaks down.