Concept of boson and fermion applied to atoms and more

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Discussion Overview

The discussion centers around the classification of atoms and molecules as bosons or fermions, particularly focusing on helium and hydrogen. Participants explore the implications of spin and the composition of these particles in determining their statistical behavior, as well as the physical properties that arise from these classifications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that helium atoms can be considered bosons due to their integer spin, while questioning why hydrogen is classified as a fermion despite having a total spin of 1.
  • Another participant explains that composite particles with an even number of fermions are bosons, while those with an odd number are fermions, citing hydrogen's composition as a basis for its classification.
  • A later reply reiterates the classification based on spin and composition, stating that hydrogen molecules (H2) consist of two bosons and are thus classified as bosons.
  • Some participants raise questions about the behavior of hydrogen molecules when they interact and why liquid hydrogen does not exhibit superfluidity like helium does.
  • There is curiosity about whether there is a size scale at which composite bosons may not exhibit bosonic properties.

Areas of Agreement / Disagreement

Participants express differing views on the classification of hydrogen and its behavior compared to helium, indicating that multiple competing views remain regarding the implications of these classifications and the physical properties associated with them.

Contextual Notes

Participants mention specific properties of hydrogen and helium, but there are unresolved questions about the conditions under which these properties manifest, particularly in relation to superfluidity and the size scale of composite bosons.

Who May Find This Useful

This discussion may be of interest to those studying quantum mechanics, statistical mechanics, or the properties of matter at low temperatures, particularly in relation to bosons and fermions.

fluidistic
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Sometime I read that the helium atoms can be considered as boson, but I don't understand why. I know that its nucleous has a spin of 2 (integer) and that its 2 electrons gives the atom a total spin of 3, an integer.
But then why isn't hydrogen considered also as a boson? I think it's considered as a fermion, like the electron itself. Why? The total spin of the H atom isn't 1 (thus an integer)? It seems like only the nucleous is the only important thing in deciding whether an atom can be considered as a boson or fermion, why is it so? And if I have a molecule, how do I determine whether it's a boson or fermion?
In Wikipedia one can read
Wiki the Great said:
(they follow different quantum statistics: helium-4 atoms are bosons while helium-3 atoms are fermions).
and also
Wiki the Giant said:
In particle physics, bosons ( /ˈboʊsɒn/[1]) are subatomic particles with integer spin (s = 0, 1, 2 etc.) that are governed by Bose-Einstein statistics.
where the enphasis is mine.
Can someone explain me when I can call a particle/atom/molecule a boson?
 
Physics news on Phys.org
It depends on spin. Composite particles with an even number of fermions is a boson with integer total spin. Particles composed of an odd number of fermions is a fermion with half-integer total spin.

A proton by itself is a fermion ( 3 quarks). A hydrogen atom has four fermions- 3 quarks and an electron- and is considered a boson.

ETA:
A hydrogen molecule (H2) consists of two bosons and is a boson.

That wiki page should read particle.
 
Last edited:
Jimmy said:
It depends on spin. Composite particles with an even number of fermions is a boson with integer total spin. Particles composed of an odd number of fermions is a fermion with half-integer total spin.

A proton by itself is a fermion ( 3 quarks). A hydrogen atom has four fermions- 3 quarks and an electron- and is considered a boson.

ETA:
A hydrogen molecule (H2) consists of two bosons and is a boson.

That wiki page should read particle.

Ok thank you very, very much! So in a way I'm either a fermion or boson. :-p
 
I'm also wondering about something related. So hydrogen molecules are bosons. However, when they interact, do they behave as bosons? Why does liquid hydrogen not display superfluidity as helium, both the 3 and 4 versions do?

Is there a size scale at which composite bosons no longer display the properties of bosons?
 
chill_factor said:
I'm also wondering about something related. So hydrogen molecules are bosons. However, when they interact, do they behave as bosons? Why does liquid hydrogen not display superfluidity as helium, both the 3 and 4 versions do?

Is there a size scale at which composite bosons no longer display the properties of bosons?

Hydrogen freezes before it can get superfluid.
 

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