## Pauli exclusion principle |

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the

**pauli exclusion principle**is the principle which states that two or morequantum mechanical identical (particles with half-integerfermions ) cannot occupy the samespin within aquantum state simultaneously. this principle was formulated by austrian physicistquantum system in 1925 for electrons, and later extended to all fermions with hiswolfgang pauli of 1940.spin–statistics theorem in the case of

in atoms, it can be stated as follows: it is impossible for two electrons of a poly-electron atom to have the same values of the fourelectrons :quantum numbers *n*, the ,principal quantum number *ℓ*, the ,azimuthal quantum number *m*, the_{ℓ} , andmagnetic quantum number *m*, the_{s} . for example, if two electrons reside in the samespin quantum number , then theirorbital *n*,*ℓ*, and*m*values are the same, therefore their_{ℓ}*m*must be different, and thus the electrons must have opposite half-integer spin projections of 1/2 and −1/2._{s}particles with an integer spin, or

, are not subject to the pauli exclusion principle: any number of identical bosons can occupy the same quantum state, as with, for instance, photons produced by abosons or atoms in alaser . this is because thebose–einstein condensate , which relates the probabilities of two similar particles entering the same state, adds the probabilities together for bosons, instead being subtracted (and thereby cancelled out) as they are for fermions.exchange interaction a more rigorous statement is that concerning the exchange of two identical particles the total

iswave function for fermions, and symmetric for bosons. this means that if the spaceantisymmetric *and*spin coordinates of two identical particles are interchanged, then the wave function changes its sign for fermions and does not change for bosons.- overview
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The **Pauli exclusion principle** is the

In the case of *n*, the *ℓ*, the *m _{ℓ}*, the

Particles with an integer spin, or

A more rigorous statement is that concerning the exchange of two identical particles the total *and* spin coordinates of two identical particles are interchanged, then the wave function changes its sign for fermions and does not change for bosons.