Two hydrogen atom with same spin can form H_2?

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Discussion Overview

The discussion centers around the conditions under which two hydrogen atoms can form a hydrogen molecule (H2), specifically focusing on the implications of their electron spins. Participants explore the relationship between spin states and molecular formation, touching on concepts from chemistry and quantum mechanics.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant asserts that hydrogen atoms must have opposite spins to form H2, questioning whether an atom can change its spin to allow for coupling.
  • Another participant distinguishes between para-hydrogen, which has opposite spins, and ortho-hydrogen, which has matching spins, suggesting that ortho-hydrogen can exist in multiple spin states.
  • A participant clarifies that their initial inquiry was about the spin of electrons rather than protons, indicating a focus on electron spin in the context of molecular formation.
  • It is noted that electrons in para-hydrogen are always opposite, while those in ortho-hydrogen can be aligned in the same direction or opposite.
  • One participant mentions that if hydrogen atoms are polarized in the same direction, the formation of H2 is likely not possible, especially under conditions of high magnetic fields and low temperatures.
  • Another participant speculates that if hydrogen were to exist in a state where all atoms are polarized in the same direction, it might exhibit different chemical properties, such as reduced density.
  • A viewpoint is presented that if two hydrogen atoms have the same spin, they cannot form H2, suggesting that only certain forces would be at play in their interactions.

Areas of Agreement / Disagreement

Participants express differing views on the role of electron and proton spins in the formation of H2. There is no consensus on whether hydrogen atoms with the same spin can form a molecule, and the discussion remains unresolved regarding the implications of spin states on molecular bonding.

Contextual Notes

Participants reference various aspects of spin coupling and molecular formation without providing definitive sources or references, indicating a reliance on memory and informal research. The discussion involves complex interactions that are not fully resolved, particularly regarding the effects of spin polarization on chemical properties.

spocchio
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As I know from the laws of chemistry,to form H_2 the H atoms must have opposite spin.
What if they have the same spin?
I mean, can an H atom rotate to swap his spin (i'm not expert of the dynamics of spin), or there is no way to couple them?
In the case I have a gas of H with all of them polarized in the same direction is the formation of H_2 possible?
 
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I believe that para-hydrogen has opposite spin, but ortho-hydrogen has matching spin.

Para-hydrogen is spin 1/2, but I believe ortho-hydrogen is allowed 3 states of spin and is a spin 1 particle.

Sorry, but I do not have a good reference on this at the moment, only memory.
 
Oh so you talk about the spin of the proton, that's another interesting subject about coupling.
I expressed myself badly, i was asking about spin of ELECTRON (i supposed chemists don't work with nuclear spin)
 
I wish I could find a handy reference, but the electrons for parahydrogen are always opposite, but the electons for ortho hydrogen can be both up, both down or opposite.

The protons for parahydrogen are always opposite, and the protons for orthohydrogen are always the same.

Does anyone have a reference to check...
 
spocchio said:
... In the case I have a gas of H with all of them polarized in the same direction is the formation of H_2 possible?

apparently not, provided that is you arrange for all the atoms to be polarized in the same direction by application of a high magnetic field at low temperatures.

sadly however all i know about the subject is what i have gleaned from googling "spin polarized atomic hydrogen" an interesting question though!
 
That's interesting. You'd then have H_1 with chemical properties that might be totally different then the familiar hydrogen. It would be half as dense, right?
 
In my opinion, if the two atoms are polarized having the same spin, they must not form the H2 which means the covalent bond can not be formed. And the interactions between the same spin will be similar to the source of van der waals force which contains dispersion force, inducing force,orientation force. Just for the atoms having the same spin, i think only the dispersion force and inducing force will work.
 

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