Why do fusion and fission both release energy?












3












$begingroup$


I only have high school physics knowledge, but here is my understanding:



Fusion: 2 atoms come together to form a new atom. This process releases the energy keeping them apart, and is very energetic. Like the sun!



Fission: Something fast (like an electron) smashes into an atom breaking it apart. Somehow this also releases energy. Less energy than fusion, and it's like a nuclear reactor.



Now my understanding is that the lowest energy state is when everything is tightly stuck together (as per fusion), and it costs energy to break them apart..



So.. why do both fusion and fission release energy?










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  • 1




    $begingroup$
    It is probably a good idea to wait a day or so before accepting an answer. It's not necessarily the case that the first answer will be the best, and the votes from the community can give you a steer in the right direction there.
    $endgroup$
    – Michael MacAskill
    38 mins ago
















3












$begingroup$


I only have high school physics knowledge, but here is my understanding:



Fusion: 2 atoms come together to form a new atom. This process releases the energy keeping them apart, and is very energetic. Like the sun!



Fission: Something fast (like an electron) smashes into an atom breaking it apart. Somehow this also releases energy. Less energy than fusion, and it's like a nuclear reactor.



Now my understanding is that the lowest energy state is when everything is tightly stuck together (as per fusion), and it costs energy to break them apart..



So.. why do both fusion and fission release energy?










share|cite|improve this question







New contributor




user230910 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$








  • 1




    $begingroup$
    It is probably a good idea to wait a day or so before accepting an answer. It's not necessarily the case that the first answer will be the best, and the votes from the community can give you a steer in the right direction there.
    $endgroup$
    – Michael MacAskill
    38 mins ago














3












3








3





$begingroup$


I only have high school physics knowledge, but here is my understanding:



Fusion: 2 atoms come together to form a new atom. This process releases the energy keeping them apart, and is very energetic. Like the sun!



Fission: Something fast (like an electron) smashes into an atom breaking it apart. Somehow this also releases energy. Less energy than fusion, and it's like a nuclear reactor.



Now my understanding is that the lowest energy state is when everything is tightly stuck together (as per fusion), and it costs energy to break them apart..



So.. why do both fusion and fission release energy?










share|cite|improve this question







New contributor




user230910 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$




I only have high school physics knowledge, but here is my understanding:



Fusion: 2 atoms come together to form a new atom. This process releases the energy keeping them apart, and is very energetic. Like the sun!



Fission: Something fast (like an electron) smashes into an atom breaking it apart. Somehow this also releases energy. Less energy than fusion, and it's like a nuclear reactor.



Now my understanding is that the lowest energy state is when everything is tightly stuck together (as per fusion), and it costs energy to break them apart..



So.. why do both fusion and fission release energy?







particle-physics nuclear-physics elements






share|cite|improve this question







New contributor




user230910 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|cite|improve this question







New contributor




user230910 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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share|cite|improve this question




share|cite|improve this question






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user230910 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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asked 2 hours ago









user230910user230910

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1163




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New contributor





user230910 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






user230910 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.








  • 1




    $begingroup$
    It is probably a good idea to wait a day or so before accepting an answer. It's not necessarily the case that the first answer will be the best, and the votes from the community can give you a steer in the right direction there.
    $endgroup$
    – Michael MacAskill
    38 mins ago














  • 1




    $begingroup$
    It is probably a good idea to wait a day or so before accepting an answer. It's not necessarily the case that the first answer will be the best, and the votes from the community can give you a steer in the right direction there.
    $endgroup$
    – Michael MacAskill
    38 mins ago








1




1




$begingroup$
It is probably a good idea to wait a day or so before accepting an answer. It's not necessarily the case that the first answer will be the best, and the votes from the community can give you a steer in the right direction there.
$endgroup$
– Michael MacAskill
38 mins ago




$begingroup$
It is probably a good idea to wait a day or so before accepting an answer. It's not necessarily the case that the first answer will be the best, and the votes from the community can give you a steer in the right direction there.
$endgroup$
– Michael MacAskill
38 mins ago










3 Answers
3






active

oldest

votes


















3












$begingroup$

Fission releases energy, because a heavy nucleus (like Uranium-235) is like a cocked mouse trap: it took energy to squeeze all those protons and neutrons hard enough together to make them barely stick (by the nuclear force) against the natural tendency for all those protons to fly violently apart because of their electrostatic repulsion. When struck by an incoming neutron, it is like a mouse touching the trigger pedal of the trap: BANG goes the nucleus.



In the case of fusion, the mechanism is different: the nuclear force between protons and between neutrons is very powerfully attractive but only kicks in when the particles are so close to each other that they are "touching". That attraction is not quite enough to stick two protons together against their electrostatic repulsion but if you add two neutrons to the recipe, you get enough mutually attractive nuclear force to overcome electrostatics and the particles then violently suck themselves together with a very powerful BANG.



Other fusion reactions in which the (2 protons plus two neutrons) get pressed onto a heavier nucleus (like carbon, nitrogen, oxygen, fluorine, ...) release progressively less energy. By the time you get to iron, further fusion reactions actually consume energy instead of releasing it, because the electrostatic repulsion effect gets bigger and bigger- and you are in the province of fission instead.






share|cite|improve this answer









$endgroup$





















    3












    $begingroup$

    Fusion:

    In a small nucleus there is a relatively large fraction of
    nucleons at the surface, which lowers the total binding energy.
    The fusion of 2 very small nuclei to one medium-sized nucleus releases energy,
    mainly because in the resulting bigger nucleus
    there are fewer nucleons at the surface than before.



    Fission:

    In a big nucleus there is much Coulomb repulsion due to the many protons.
    The fission of a very big nucleus into 2 medium-sized nuclei releases energy,
    mainly because the total Coulomb repulsion within the 2 resulting
    nuclei is smaller than before.



    Therefore, medium-sized nuclei (~ 55 nucleons) have the biggest binding energy per nucleon.



    The Bethe-Weizsäcker formula for the binding energy of a nucleus
    gives a more quantitative explanation for this.






    share|cite|improve this answer











    $endgroup$





















      2












      $begingroup$

      Your assumption about the lowest energy state when everything is tightly stuck together is incorrect.



      It only goes this way until you get iron nuclei - and this is why iron is the heaviest element created by fusion.



      Creating nuclei heavier than iron consumes energy rather than releasing it. And this is why these elements are only created in supernova explosions and other highly energetic events where there is abundant energy input.






      share|cite|improve this answer









      $endgroup$













      • $begingroup$
        The nuclear binding energy diagram shows this fact very nicely
        $endgroup$
        – WorldSEnder
        10 mins ago











      Your Answer





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      3 Answers
      3






      active

      oldest

      votes








      3 Answers
      3






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      3












      $begingroup$

      Fission releases energy, because a heavy nucleus (like Uranium-235) is like a cocked mouse trap: it took energy to squeeze all those protons and neutrons hard enough together to make them barely stick (by the nuclear force) against the natural tendency for all those protons to fly violently apart because of their electrostatic repulsion. When struck by an incoming neutron, it is like a mouse touching the trigger pedal of the trap: BANG goes the nucleus.



      In the case of fusion, the mechanism is different: the nuclear force between protons and between neutrons is very powerfully attractive but only kicks in when the particles are so close to each other that they are "touching". That attraction is not quite enough to stick two protons together against their electrostatic repulsion but if you add two neutrons to the recipe, you get enough mutually attractive nuclear force to overcome electrostatics and the particles then violently suck themselves together with a very powerful BANG.



      Other fusion reactions in which the (2 protons plus two neutrons) get pressed onto a heavier nucleus (like carbon, nitrogen, oxygen, fluorine, ...) release progressively less energy. By the time you get to iron, further fusion reactions actually consume energy instead of releasing it, because the electrostatic repulsion effect gets bigger and bigger- and you are in the province of fission instead.






      share|cite|improve this answer









      $endgroup$


















        3












        $begingroup$

        Fission releases energy, because a heavy nucleus (like Uranium-235) is like a cocked mouse trap: it took energy to squeeze all those protons and neutrons hard enough together to make them barely stick (by the nuclear force) against the natural tendency for all those protons to fly violently apart because of their electrostatic repulsion. When struck by an incoming neutron, it is like a mouse touching the trigger pedal of the trap: BANG goes the nucleus.



        In the case of fusion, the mechanism is different: the nuclear force between protons and between neutrons is very powerfully attractive but only kicks in when the particles are so close to each other that they are "touching". That attraction is not quite enough to stick two protons together against their electrostatic repulsion but if you add two neutrons to the recipe, you get enough mutually attractive nuclear force to overcome electrostatics and the particles then violently suck themselves together with a very powerful BANG.



        Other fusion reactions in which the (2 protons plus two neutrons) get pressed onto a heavier nucleus (like carbon, nitrogen, oxygen, fluorine, ...) release progressively less energy. By the time you get to iron, further fusion reactions actually consume energy instead of releasing it, because the electrostatic repulsion effect gets bigger and bigger- and you are in the province of fission instead.






        share|cite|improve this answer









        $endgroup$
















          3












          3








          3





          $begingroup$

          Fission releases energy, because a heavy nucleus (like Uranium-235) is like a cocked mouse trap: it took energy to squeeze all those protons and neutrons hard enough together to make them barely stick (by the nuclear force) against the natural tendency for all those protons to fly violently apart because of their electrostatic repulsion. When struck by an incoming neutron, it is like a mouse touching the trigger pedal of the trap: BANG goes the nucleus.



          In the case of fusion, the mechanism is different: the nuclear force between protons and between neutrons is very powerfully attractive but only kicks in when the particles are so close to each other that they are "touching". That attraction is not quite enough to stick two protons together against their electrostatic repulsion but if you add two neutrons to the recipe, you get enough mutually attractive nuclear force to overcome electrostatics and the particles then violently suck themselves together with a very powerful BANG.



          Other fusion reactions in which the (2 protons plus two neutrons) get pressed onto a heavier nucleus (like carbon, nitrogen, oxygen, fluorine, ...) release progressively less energy. By the time you get to iron, further fusion reactions actually consume energy instead of releasing it, because the electrostatic repulsion effect gets bigger and bigger- and you are in the province of fission instead.






          share|cite|improve this answer









          $endgroup$



          Fission releases energy, because a heavy nucleus (like Uranium-235) is like a cocked mouse trap: it took energy to squeeze all those protons and neutrons hard enough together to make them barely stick (by the nuclear force) against the natural tendency for all those protons to fly violently apart because of their electrostatic repulsion. When struck by an incoming neutron, it is like a mouse touching the trigger pedal of the trap: BANG goes the nucleus.



          In the case of fusion, the mechanism is different: the nuclear force between protons and between neutrons is very powerfully attractive but only kicks in when the particles are so close to each other that they are "touching". That attraction is not quite enough to stick two protons together against their electrostatic repulsion but if you add two neutrons to the recipe, you get enough mutually attractive nuclear force to overcome electrostatics and the particles then violently suck themselves together with a very powerful BANG.



          Other fusion reactions in which the (2 protons plus two neutrons) get pressed onto a heavier nucleus (like carbon, nitrogen, oxygen, fluorine, ...) release progressively less energy. By the time you get to iron, further fusion reactions actually consume energy instead of releasing it, because the electrostatic repulsion effect gets bigger and bigger- and you are in the province of fission instead.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered 1 hour ago









          niels nielsenniels nielsen

          17.9k42757




          17.9k42757























              3












              $begingroup$

              Fusion:

              In a small nucleus there is a relatively large fraction of
              nucleons at the surface, which lowers the total binding energy.
              The fusion of 2 very small nuclei to one medium-sized nucleus releases energy,
              mainly because in the resulting bigger nucleus
              there are fewer nucleons at the surface than before.



              Fission:

              In a big nucleus there is much Coulomb repulsion due to the many protons.
              The fission of a very big nucleus into 2 medium-sized nuclei releases energy,
              mainly because the total Coulomb repulsion within the 2 resulting
              nuclei is smaller than before.



              Therefore, medium-sized nuclei (~ 55 nucleons) have the biggest binding energy per nucleon.



              The Bethe-Weizsäcker formula for the binding energy of a nucleus
              gives a more quantitative explanation for this.






              share|cite|improve this answer











              $endgroup$


















                3












                $begingroup$

                Fusion:

                In a small nucleus there is a relatively large fraction of
                nucleons at the surface, which lowers the total binding energy.
                The fusion of 2 very small nuclei to one medium-sized nucleus releases energy,
                mainly because in the resulting bigger nucleus
                there are fewer nucleons at the surface than before.



                Fission:

                In a big nucleus there is much Coulomb repulsion due to the many protons.
                The fission of a very big nucleus into 2 medium-sized nuclei releases energy,
                mainly because the total Coulomb repulsion within the 2 resulting
                nuclei is smaller than before.



                Therefore, medium-sized nuclei (~ 55 nucleons) have the biggest binding energy per nucleon.



                The Bethe-Weizsäcker formula for the binding energy of a nucleus
                gives a more quantitative explanation for this.






                share|cite|improve this answer











                $endgroup$
















                  3












                  3








                  3





                  $begingroup$

                  Fusion:

                  In a small nucleus there is a relatively large fraction of
                  nucleons at the surface, which lowers the total binding energy.
                  The fusion of 2 very small nuclei to one medium-sized nucleus releases energy,
                  mainly because in the resulting bigger nucleus
                  there are fewer nucleons at the surface than before.



                  Fission:

                  In a big nucleus there is much Coulomb repulsion due to the many protons.
                  The fission of a very big nucleus into 2 medium-sized nuclei releases energy,
                  mainly because the total Coulomb repulsion within the 2 resulting
                  nuclei is smaller than before.



                  Therefore, medium-sized nuclei (~ 55 nucleons) have the biggest binding energy per nucleon.



                  The Bethe-Weizsäcker formula for the binding energy of a nucleus
                  gives a more quantitative explanation for this.






                  share|cite|improve this answer











                  $endgroup$



                  Fusion:

                  In a small nucleus there is a relatively large fraction of
                  nucleons at the surface, which lowers the total binding energy.
                  The fusion of 2 very small nuclei to one medium-sized nucleus releases energy,
                  mainly because in the resulting bigger nucleus
                  there are fewer nucleons at the surface than before.



                  Fission:

                  In a big nucleus there is much Coulomb repulsion due to the many protons.
                  The fission of a very big nucleus into 2 medium-sized nuclei releases energy,
                  mainly because the total Coulomb repulsion within the 2 resulting
                  nuclei is smaller than before.



                  Therefore, medium-sized nuclei (~ 55 nucleons) have the biggest binding energy per nucleon.



                  The Bethe-Weizsäcker formula for the binding energy of a nucleus
                  gives a more quantitative explanation for this.







                  share|cite|improve this answer














                  share|cite|improve this answer



                  share|cite|improve this answer








                  edited 55 mins ago

























                  answered 1 hour ago









                  Thomas FritschThomas Fritsch

                  37929




                  37929























                      2












                      $begingroup$

                      Your assumption about the lowest energy state when everything is tightly stuck together is incorrect.



                      It only goes this way until you get iron nuclei - and this is why iron is the heaviest element created by fusion.



                      Creating nuclei heavier than iron consumes energy rather than releasing it. And this is why these elements are only created in supernova explosions and other highly energetic events where there is abundant energy input.






                      share|cite|improve this answer









                      $endgroup$













                      • $begingroup$
                        The nuclear binding energy diagram shows this fact very nicely
                        $endgroup$
                        – WorldSEnder
                        10 mins ago
















                      2












                      $begingroup$

                      Your assumption about the lowest energy state when everything is tightly stuck together is incorrect.



                      It only goes this way until you get iron nuclei - and this is why iron is the heaviest element created by fusion.



                      Creating nuclei heavier than iron consumes energy rather than releasing it. And this is why these elements are only created in supernova explosions and other highly energetic events where there is abundant energy input.






                      share|cite|improve this answer









                      $endgroup$













                      • $begingroup$
                        The nuclear binding energy diagram shows this fact very nicely
                        $endgroup$
                        – WorldSEnder
                        10 mins ago














                      2












                      2








                      2





                      $begingroup$

                      Your assumption about the lowest energy state when everything is tightly stuck together is incorrect.



                      It only goes this way until you get iron nuclei - and this is why iron is the heaviest element created by fusion.



                      Creating nuclei heavier than iron consumes energy rather than releasing it. And this is why these elements are only created in supernova explosions and other highly energetic events where there is abundant energy input.






                      share|cite|improve this answer









                      $endgroup$



                      Your assumption about the lowest energy state when everything is tightly stuck together is incorrect.



                      It only goes this way until you get iron nuclei - and this is why iron is the heaviest element created by fusion.



                      Creating nuclei heavier than iron consumes energy rather than releasing it. And this is why these elements are only created in supernova explosions and other highly energetic events where there is abundant energy input.







                      share|cite|improve this answer












                      share|cite|improve this answer



                      share|cite|improve this answer










                      answered 1 hour ago









                      cuckoocuckoo

                      994




                      994












                      • $begingroup$
                        The nuclear binding energy diagram shows this fact very nicely
                        $endgroup$
                        – WorldSEnder
                        10 mins ago


















                      • $begingroup$
                        The nuclear binding energy diagram shows this fact very nicely
                        $endgroup$
                        – WorldSEnder
                        10 mins ago
















                      $begingroup$
                      The nuclear binding energy diagram shows this fact very nicely
                      $endgroup$
                      – WorldSEnder
                      10 mins ago




                      $begingroup$
                      The nuclear binding energy diagram shows this fact very nicely
                      $endgroup$
                      – WorldSEnder
                      10 mins ago










                      user230910 is a new contributor. Be nice, and check out our Code of Conduct.










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