Exclusion principles for fermions and bosons

In summary, the exclusion principle applies to fermions and bosons differently as fermions cannot be in the same state of motion while bosons do not follow this rule. Two electrons, being identical fermions, cannot be in the same state of motion due to their spin being different, even if they are in different atoms. The eigenstates of electrons are always a combination of orbitals from different atoms, making it impossible for two electrons to be in the same state of motion.
  • #1
Brandon1994
9
0
Hello,
I was curious about how the exclusion principle applied to fermions and bosons differently. My current understanding is that the exclusion principle states that no two fermions may be in the same state of motion and that bosons do not obey the exclusion principle. My problem with this is can't two electrons (identical fermions) be in the same state of motion? I know that no two electrons may be described by the same four quantum numbers in the same atom, however, isn't it possible for two electrons in different atoms ( or for the sake of argument two free electrons ) to be in the same state of motion? How does this not violate the exclusion principle?


~thanks
 
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  • #2
They cannot be identical in all quantum numbers. They can have the same spatial wave function ("state of motion"?), if their spin is different, for example.

Electrons are identical - if you consider two atoms, you cannot say "this electron is at atom A and that electron is at atom B". The eigenstates are always combinations of "orbital at atom A" + "orbital at atom B" (plus some modification if the atoms are close to each other), and both electrons will be in different eigenstates.
 
  • #3
Im not that up on quantum theory ( I am starting college as a physics major and have only completed ap level high school physics and single variable calculus ) but if I understand correctly, you are saying that two electrons are in different states of motion due to the fact that they are in different orbitals? (Im guessing the eigenstate function involves the orbital)
 

Related to Exclusion principles for fermions and bosons

1. What is an exclusion principle?

An exclusion principle is a physical rule that states that certain types of particles cannot occupy the same quantum state at the same time. This means that two particles cannot have identical values for all of their quantum numbers, such as spin, energy, and position.

2. What is the difference between fermions and bosons?

Fermions and bosons are two types of particles that follow different exclusion principles. Fermions are particles with half-integer spin, such as electrons, protons, and neutrons. They follow the Pauli exclusion principle, which states that no two fermions can occupy the same quantum state. Bosons, on the other hand, have integer spin, such as photons and gluons. They follow the Bose-Einstein exclusion principle, which allows multiple particles to occupy the same quantum state.

3. Why do fermions follow the Pauli exclusion principle?

Fermions follow the Pauli exclusion principle because they are governed by the laws of quantum mechanics, which state that no two particles can have the same set of quantum numbers. This is due to the wave nature of fermions, which leads to a phenomenon called wave function collapse. When two fermions with the same quantum state come into contact, their wave functions collapse, resulting in different quantum states.

4. How does the exclusion principle affect the properties of matter?

The exclusion principle plays a crucial role in determining the properties of matter. For example, the Pauli exclusion principle is responsible for the electron configuration of atoms, which determines their chemical properties. It also explains why matter is stable and does not collapse into a single point, as fermions cannot occupy the same space. Additionally, the Bose-Einstein exclusion principle is responsible for phenomena such as superconductivity and superfluidity.

5. Are there any exceptions to the exclusion principle?

While the exclusion principle holds true for most particles, there are a few exceptions. For example, quarks, which are the building blocks of protons and neutrons, can have the same quantum numbers due to their color charge. Additionally, in certain extreme conditions, such as in black holes, the exclusion principle may not apply. However, these exceptions are rare and do not significantly impact the overall validity of the exclusion principles for fermions and bosons.

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