Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Binding Energy-same question-different approach

  1. Aug 24, 2007 #1
    OK, I think I have discovered some errors in my thinking about this whole binding energy/release of energy thing. In my other threads, however, you guys often left the subject of my question to explain the next concept (quarks, stellar formations, Q-factors, etc.) The problem was I never understood what the answer to my question was. I can get very "wordy" at times, so this time I will ask VERY DIRECT questions, so please try to give VERY DIRECT answers--yes or no answers if possible. I will never get to the more advanced concepts if I don't get this release of energy thing down.

    I think where I have been confused is by WHAT ENERGY does the actual holding together (binding??) of the newly-formed nucleus. I HAD thought that the energy to do this CAME OUT OF THE MISSING MASS OR BINDING ENERGY--taken AWAY from the 28.3MeV and sunk into the nucleus, to hold it together. I now feel that perhaps it is the "nuclear force" that holds the nucleus together on a permanent basis. I now think "nuclear force" is an entirely different entity than the missing mass energy and/or the binding energy.

    OK, here we go:

    1.) Are "missing mass energy" and "binding energy" different names for the same entity??

    2.) Is the "nuclear force" a completely different entity than the "missing mass energy" and/or the "binding energy"?? I am not concerned now if one causes the other or not--I merely want to know if they are the same individual or different individuals.

    Hopefully I can better word my questions this time around, so it is obvious what part I don't understand. You folks are awesome---many thanks!
  2. jcsd
  3. Aug 24, 2007 #2
    I actually find this kind of confusing too, but it is a bit clearer if you draw a parallel between binding energy and bonding... two hydrogens and an oxygen separated have more mass than H20, the reason for this is that the bonds between the atoms require energy, and this energy comes from a small amount of missing mass (so small that it is practically unmeasurable)... the repulsion between protons in the nucleus practically on top of each other is a lot greater and thus requires a lot more energy which also comes from mass. These parallels make certain concepts less foreign, the energy going off in a nuke is the same as the energy going off in an exothermic chemical reaction, the energy in the bonds is just vastly different. Now to your questions, the missing mass energy (same thing as binding energy) is the supply of energy for the nuclear force.
    Last edited: Aug 24, 2007
  4. Aug 24, 2007 #3
    Hmmmm--if the "missing mass" energy is what supplies the "nuclear force", then it seems to me there would be zero "nuclear force", until the "missing mass" energy arrived. But, I thought the "nuclear force" is what finished up the drawing together of the nucleons, after we pushed them close enough together for the "nuclear force" to overpower the Coulomb Effect (2 positives repel each other). As this final distance is being closed, nothing has binded yet, but the "Nuclear Force" is still drawing them together. In other words, it seems to me that there is a "nuclear force" long before there is any "missing mass".

    1.) Does the "nuclear force" exist before the mass goes missing, at the same instant as the mass goes missing, or after the mass goes missing?
  5. Aug 25, 2007 #4


    User Avatar
    Science Advisor
    Homework Helper

    Potaire: Have you tried to do some calculation to see that energy is released when you fuse togheter 2 protons using kinetic energy just to get over the columb-repulsion. And compare to the total energy you get on the other side; one Helium-2 nucleus.

    Alos try to do some calculation on neutron induced fission.

    And yes "missing mass energy" and "binding energy" is same thing. Binding energy is defined to be the missing mass energy.

    And The nuclear force is a very complicated subject, even for last year undergrad stud in theoretical nuclear physics. So I would not recomend you, at the moment, to try to investigate what that force is, because we dont know so well yet =)

    Compare with the hydrogen atom, the binding energy is approx 13eV (in nucleis several MeV) and this force we know well, the electromagnetic force. But this force is not due to the lost mass of the electron and proton (Iam now talking about the hydrogen atom), but is a fundemental property of the objects.
  6. Aug 25, 2007 #5
    malawi: I've tried some math already. Getting 28.3MeV from a d-->d fusion was easy. I have seen the d-->t=17.6MeV yield thing done, but not sure that I understand it. That's about all I have tried. That's about all my understanding will ALLOW me to try, at this point.

    My question about the timing of Nuclear Force was not really a question for me. It was for Spitfire himself. He stated that the Missing-Mass Force is what powers the Nuclear Force. I think that is wrong, is it not? My question tried to point out that Nuclear Force existed BEFORE there WAS any Missing-Mass Force, therefore the Missing Mass Force could NOT power the Nuclear Force. IF I AM WRONG ABOUT THIS PART PLEASE TELL ME!!! THIS IS WHERE ALL MY PROBLEMS CAME FROM--WHAT FORCE IS IT THAT HOLDS NUCLEONS TOGETHER, NUCLEAR FORCE OR MISSING-MASS FORCE. I did find a cool site, using "nuclear force" in Google. It explains that it is one of the Four Basic Forces in the Universe. It also explains that "mesons" are what make the Nuclear Force function. It was fairly easy to follow at the level they presented it. But, it makes clear (to me, anyways) that Nuclear Force is it's own entity, not powered by Missing-Mass Forse. Check it out:

    OK, now we see if I have made any progress. Please answer TRUE or FALSE

    1). The Nuclear Force is what holds the nucleons together, resulting in the Helium atom. The missing mass from fusion is converted into a different force or energy, which is called "Missing-Mass Energy", or also called "Binding Energy". NONE OF THIS "MISSING-MASS ENERGY/BINDING ENERGY" IS USED TO HOLD THE NUCLEONS TOGETHER IN THE NUCLEUS--THAT IS ACCOMPLISHED BY THE NUCLEAR FORCE.

    I am praying I finally have this right!!! :)

    My next official question will be right up your alley, malawi--I am wondering what connection is there between the 28.3MeV and the 17.6MeV? I know the 17.6 is a d-->t fusion, not a d-->d fusion like the 28.3. Let's save it until I am sure about what we are discussing on this page--what energy holds the nucleaons together.
  7. Aug 25, 2007 #6


    User Avatar
    Science Advisor
    Homework Helper

    Yes that is quite right. The Nuclear Force is what holds the nucleons together, the missing mass is liberated other kinds of energy.

    The meson exchange model is one of the models, yes.

    And energy does not hold things together, forces does.

    And what kind of connection are you talking about regarding 17.6 and 28.3 MeV ?
  8. Aug 25, 2007 #7
    Excellent!! Perhaps I can make some forward progress now.

    I'm not sure what kind of connection between 17.6 and 28.3 I mean. The 28.3 is the Mising-Mass Energy from a d-->d fusion, correct? And the 17.6 is the energy returned to us in a d-->t fusion, correct? I THINK what I am getting at is how to go from the initial Missing-Mass energy to the energy left over for us, or the yield. I am guessing that the yield in the d-->d fusion would be way less than 13.6---taking an educated guess I'd say 3.5MeV???????? (I saw that in a chart that divided up the 17.6 into energy from the Helium atom and energy from the extra neutron) I would love to learn how to calculate the yield from fusion of any different combo of elements chosen. As Astronuc taught me, I understand it is not just one simple step and it is done. Often protons must be "castrated" first, in order to provide the neutrons needed for fusion. A few examples of yield from, say carbon-lithium fusion, or helium-oxygen fusion, or even an iron-iron fusion, which would yield very close to zero (so it is said). The math part is no problem--almost had enough math for a Minor in college--but I need to know where to get the numbers, and which ones go where in an equation. The math part is actually fun to me!
  9. Aug 25, 2007 #8
    I MIGHT see the answer to my own question. 28.3MeV is the theoretical yield from a p-->n-->p-->n=He4. The missing mass is the diff between the total of the 4 individual masses, minus the Helium mass, times 931.494=28.3. But, as Astronuc said, that is theory only--it doesn't happen that way in real life. In real life you must first fuse a deutrium, then fuse a tritrium, and only THEN can you fuse a deutrium with a tritrium to make this work. Well, some of that theoretical 28.3 was already released to fuse the p-->n=deutrium (2.224408 was used). And some MORE of the 28.3 was already released to fuse the p-->n-->n=tritrium (8.482184) What is left over is the 17.6MeV, which is the real-life yield from the fusion of deutrium-->tritrium=He4 + a left-over neutron (d-->t=He4 + n)

    2.) This is what you were trying to get at, right Astronuk?? Theory vs reality??
    Last edited: Aug 25, 2007
  10. Aug 25, 2007 #9


    User Avatar
    Science Advisor
    Homework Helper

    The 28.3 MeV etc is not theoretically derived, the numbers are calculated by comparing masses of the constituents and the total nuclei.

    And when you calculate the energy-yeild in fusion, you must take into account the gamow-factor etc..

    And yes, as Astronuc said, you must add energy to get the two nucleons togheter close, and therefore you need to suply energy to overcome the columb repulsion (if we are talking charged nucleons/nucleis). But the energy you put in is, in general, much smaller then the energy relased in the fusion process (binding energy).
  11. Aug 25, 2007 #10
    I guess I worded that wrong (again)! I did not mean the numbers were theoretical--the numbers are pure math, and very little of math is theory! :) I meant the whole process of getting the 4 seperate and individual nucleons together and fusing them into Helium in one simple step was theoretical. If it was to be actually done, it would release 28.3MeV. But here on Earth it can not be done so simply. It requires 3 steps instead of one:
    1--fuse a proton and a neutron to make deutrium some energy released (2.22MeV)
    2--fuse a proton and 2 neutrons to make tritrium some energy released (8.48MeV)
    3--fuse the deutrium and the tritrium=He4 + n all remaining energy released (17.6MeV)

    Notice the individual releases total up to our 28.3. So, when we do this in real life here on Earth, the 28.3MeV is NOT released all at once, but instead divided up and released in three different steps. The last step is what makes holes in Nevada deserts (17.6MeV). Do I understand this correctly, more-or-less?
  12. Aug 25, 2007 #11
    im sorry Potaire, I guess my false analogies have left me with an incorrect understanding of what's going on... Is binding energy just electrical potential energy then?
  13. Aug 25, 2007 #12
    No problem, Spitfire. Believe me, I am certainly NOT someone to do the explaining!!!! Look at all the shattered threads I have left in my wake, all in quest of an answer to the ONE TRUE QUESTION. That question was: """Is the Binding Energy-aka Missing Mass Energy--responsible for holding the nucleus of the new atom together?""" I struggled to find that out one way or another, despite all the help I was given. Finally, a couple days ago, I feel I hit the answer. For better or worse, I will attempt to explain what I now THINK happens. The answer is """NO""". The Binding Energy/Missing Mass Energy does NOT hold the nucleus together. The nucleus is held together by the mysterious "Nuclear Force", which is the same force that sucked the parts together in the first place, to form the nucleus. However, at first other forces were working AGAINST the Nuclear Force, and trying to keep those parts away from each other. This "bad guy" force is the electomagnetic repelling power that pushes apart two objects with the same electric charge--both positive in the case of our protons. This "bad guy" is called the "Coulomb Barrier". Luckily, there is a distance at which the Nuclear Force can overpower the Coulomb Barrier, and suck the protons together anyways. It is our job to get those protons close enough together for the Nuclear Force to do this (heat, from an Atom Bomb, pushes them together enough for us). This Nuclear Force does NOT require any Missing Mass Energy/Binding Energy to do it's work--it has it's own Force. Now that the protons are stuck together, they will remain that way, until someday the proper amount of energy from FISSION is applied to overpower the Nuclear Force and break them apart again.

    The Missing Mass Energy/Binding Energy plays no part in holding the nucleus together, and is a completely different thing from this Nuclear Force.

    The Missing Mass Energy/Binding Energy is generated from the missing mass! The missing mass was CONVERTED into energy according to Einstein's E=MCsquared. THIS is the energy that we get back (some of it, anyways) to make holes in the ground. And this energy that we get back is WAY MORE than the energy we supplied from the Atom Bomb. The Atom Bomb was only necessary to "light the fuse" of the Hydrogen Bomb, so to speak. The Atom Bomb is what helped the Nuclear Force achieve victory over the Coulomb Barrier. Without that victory, fusion never even can get started. I must say, however, I think the name "BINDING Energy" is a very poor choice of a name for the Missing Mass Energy. "Binding Energy" certainly implies that it is used to bind the nucleus together---that is what I thought for so long, and what caused me so many problems.

    It will probably be the case that someone comes in and says I am completely full of s_ _ t, and I don't understand any of this any better than does a Goonie Bird!! So be prepared to delete all of what I have said from your memory!! :) :) :)
  14. Aug 25, 2007 #13
    ok, try this interpretation, in which missing mass energy and binding energy are different, but that connects well all the things I learned about these processes...
    so these protons are jammed together... now two things happen... first of all some mass is turned into energy (missing mass energy), this energy is released... this is fusion... second the protons gain a tremendous amount of electrical potential energy (same as when 2 masses gain gravitational PE when separated, then when you let go so to speak, and let them come together again, they release something called "gravitational binding energy", which is just gravitational PE -> KE, the KE is mostly in the form of heat... this is from wikipedia... http://www.google.com/search?hl=en&oi=definer&q=define:gravitational+binding+energy&defl=en) well in the case of fission, when the nuclear force is overcome, the protons release electrical binding energy which is just the protons turning that electrical PE (which has been stored up ever since the nuclei formed) into KE (heat, light... the stuff of atom bombs) as they get farther apart... that's fission....
    I don't know if the terminology is all right but this all sounds correct to me, don't you think so?
    Last edited: Aug 25, 2007
  15. Aug 25, 2007 #14
    Spitfire, I would have no clue if potential electric energy enters into this or not--I am still waiting for someone to tell me I am correct on my own theory so far!! :) :) :) I do think you unintenionally said, in your first sentence, "missing mass energy and binding energy are different" Untrue--even by your own words way up there. They are same thing. I think what you meant to say is that it is the Nuclear Force that is different from the missing mass/binding energy. Check out that link I left way up the page, on post #5. I think it does a great job explaining the Nuclear Force in a way rookies can understand.
    Last edited: Aug 25, 2007
  16. Aug 25, 2007 #15
    Astronuc----I hope you are following this thread, and are not burned out on my difficulties. Many of the things you tried to teach me, in the previous thread, make perfect sense to me now. Judging from THIS thread, do you think I have turned the corner and finally understand this very first step of fusion?
  17. Aug 26, 2007 #16
    I like my second interpretation better, it makes a lot of sense... especially after I looked up the term binding energy =)... in any case I think that everything I wrote in that last post is true, though I may be wrong (again)... you may have better luck googling these terms
  18. Aug 26, 2007 #17
    The potential energy stuff is over my head at the moment. Sounds like you're on top of it, tho. Are you sure you meant to say that "missing mass energy and binding energy are different"?? (very top line of post #13)
  19. Aug 26, 2007 #18


    User Avatar
    Staff Emeritus
    Science Advisor

    No problem - I've been on vacation the last 4 days. I get onto this thread and work on the other as well. :smile:
  20. Aug 26, 2007 #19
    Astronuc----Right on, and welcome back. This thread shows completely different thoughts as compared to my last thread. I am especially interested in your take on my post #8, #10, and #12 here on this thread. #8 and #10 I played with some math, while in #12 I tried to explain what I now THINK is the whole general concept. Are these 3 posts more-or-less correct statements/explanations? I am sure I must be closer to the truth than in my last thread--which revolved around the thought of taking energy AWAY from the 28.3 MeV to "glue" the nucleons together in the new alpha particle. That thought led to my wondering "where does the energy for us come from?" if all 28.3 was used for glue! I see now (hopefully) that I did not consider the "nuclear force" back then (probably cuz I had yet to hear of it!! lol ).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook