Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    12
    ReputationRep:
    Probably lazy, but I figured this might be faster than googling them:

    Why are protons stable and neutrons not? What factors broadly affect stability of hadrons?

    How does pion exchange work between nucleons? What causes the nucleon to give off a pion (interpret the word 'cause' loosely).

    Edit: to clarify this question the specific things I'm having trouble finding an explanation for are: how does the strong force (which acts on colour) cause an attraction between colour-neutral nucleons, by the exchange of colour neutral pions? Also, it would be really nice if someone could present a step by step version of what happens, although if that's impossible then it would be good to know that as well.

    Why do pretty much all nuclides have more neutrons than protons?

    Edit: I can't find a good answer for this online. My guess is that more neutrons bring an extra bit of stability to a nuclide by increasing the separation between positively charged protons. But I can't find anything to back that up, or suggest otherwise. Simple confirmation/negation would be nice.

    Thanks, would be interesting to know a bit more about this topic.
    • Study Helper
    Online

    21
    ReputationRep:
    Study Helper
    (Original post by lerjj)
    Probably lazy, but I figured this might be faster than googling them:

    Why are protons stable and neutrons not? What factors broadly affect stability of hadrons?

    How does pion exchange work between nucleons? What causes the nucleon to give off a pion (interpret the word 'cause' loosely).

    Why do pretty much all nuclides have more neutrons than protons?

    Thanks, would be interesting to know a bit more about this topic.
    Don't be lazy lerjj, the truth is out there. Put some effort in man!
    Offline

    5
    ReputationRep:
    (Original post by lerjj)
    ..
    Question 1

    Question 2

    Question 3

    I got your back man.


    (Original post by uberteknik)
    Don't be lazy lerjj, the truth is out there. Put some effort in man!
    The effort is now minimal, lerjj will make it through this.
    • Study Helper
    Online

    21
    ReputationRep:
    Study Helper
    (Original post by Phichi)



    The effort is now minimal, lerjj will make it through this.
    I love LMGTFY !
    • Thread Starter
    Offline

    12
    ReputationRep:
    (Original post by Phichi)
    Question 1

    Question 2

    Question 3

    I got your back man.




    The effort is now minimal, lerjj will make it through this.
    Wow. I deserved that...

    Is there any chance you actually checked what results those searches gave? Because they're not very helpful BTW. For instance, the first search result comes up primarily with details about why nuclides are stable, not why nucleons are/ are not. And their explanation of why they are stable seems to rest mainly on "it's magic!" (not really, but close enough).
    Offline

    13
    ReputationRep:
    (Original post by lerjj)
    Why are protons stable and neutrons not? What factors broadly affect stability of hadrons?
    Put simply: you know how the universe, as a whole, favours the lowest-energy possible states? Hence why electrons fill from the centre up, why things fall down to Earth etc. This is entropy encapsulated. Essentially, low energy = stable. This is logical because, to go from low to high energy, work must be done. Inversely, then, systems will spontaneously tunnel from high to low energy until it becomes stable.

    Now, protons are stable because baryon number is a conserved quantity, and protons are the baryons with the least mass-energy. Neutrons, however, have slightly greater rest mass than protons, so, after an indeterminate amount of time, neutrons will decay into protons. Protons can't decay because they are already the lowest-energy baryon which exists.

    What factor broadly affects stability of hadrons? Generally, in terms of stability and decay, it's all about the energy of a system. Systems at high energy decay into lower-energy states. Equivalently, particles of high mass will decay into particles of lower mass. This is partly why W bosons, for instance, have such incredibly short lifespans: they're incredibly massive. To understand more about this particular scenario, the uncertainty principle actually comes into play by considering energy and time as conjugate variables.
    • Thread Starter
    Offline

    12
    ReputationRep:
    (Original post by sjgriffiths)
    Put simply: you know how the universe, as a whole, favours the lowest-energy possible states? Hence why electrons fill from the centre up, why things fall down to Earth etc. This is entropy encapsulated. Essentially, low energy = stable. This is logical because, to go from low to high energy, work must be done. Inversely, then, systems will spontaneously tunnel from high to low energy until it becomes stable.

    Now, protons are stable because baryon number is a conserved quantity, and protons are the baryons with the least mass-energy. Neutrons, however, have slightly greater rest mass than protons, so, after an indeterminate amount of time, neutrons will decay into protons. Protons can't decay because they are already the lowest-energy baryon which exists.

    What factor broadly affects stability of hadrons? Generally, in terms of stability and decay, it's all about the energy of a system. Systems at high energy decay into lower-energy states. Equivalently, particles of high mass will decay into particles of lower mass. This is partly why W bosons, for instance, have such incredibly short lifespans: they're incredibly massive. To understand more about this particular scenario, the uncertainty principle actually comes into play by considering energy and time as conjugate variables.
    Is there a reason for the mass difference, or is this simply because down quarks are more massive than up quarks and so neutrons just ARE heavier? (I.e. is this the only/most significant factor at play? Or is uud somehow more stable because it forms stronger bonds than udd, or some other explanation.)

    Thanks for the help!
    Offline

    13
    ReputationRep:
    (Original post by lerjj)
    Is there a reason for the mass difference, or is this simply because down quarks are more massive than up quarks and so neutrons just ARE heavier? (I.e. is this the only/most significant factor at play? Or is uud somehow more stable because it forms stronger bonds than udd, or some other explanation.)

    Thanks for the help!
    Yes, down quarks are the lightest of all quarks, whilst up quarks come a close second. So just by their composition, neutrons are slightly more massive than protons.

    I'm not aware of the strong interaction itself causing any differences in the stability of either hadrons or nuclei. It pretty much all comes down to the mass-energy of the constituents.

    No problem!
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Would you rather give up salt or pepper?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Write a reply...
    Reply
    Hide
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.