Nuclear Reactions

When nuclei of atoms come close enough together they can interact and produce a powerful reaction.  These reactions can either be endothermic or exothermic.  There are two main types of reactions and they are fusion and fission.

Fusion

Fusion is the combination of two light nuclei for for a single heavier nucleus.  An example of this is the combination of two different hydrogen isotopes for form a single isotope of helium.  The results of this reaction is an enormous amount of energy that is liberated form the system.  This happens because the combined mass of the two lighter nuclei is more than the mass of the product nuclei.  Since there is a loss of mass then energy is created.  Which is where the huge amount of energy comes from.  These reactions do not occur naturally on earth because of the large amount of energy required to cause the two nuclei to fuse.  There is a very large electrostatic force that repels the two positively charged nuclei so getting the close enough to fuse requires a tremendous amount of energy.  The closest fusion reaction that a person on earth can witness is the sun.  Fusion reactions can be produced in laboratories on earth and these experiments led to the creation of some of the first thermonuclear fusion weapons, i.e. hydrogen bombs.

Fig 9

Fission

Fission is the splitting of a heavy nucleus into two smaller nuclei.  Any combination of smaller nuclei can be produced in a fission reactions as long as the number of protons and neutrons add up the amount in the initial nucleus.  Fission actually occurs because the repulsion of all of the positively charged protons that are in the heavy nucleus.  When the larger nucleus overcomes the strong nuclear force they split and a large amount of energy is given off.  Like fusion, fission can be used to create very power nuclear bombs, but it can also be used to create energy.  Nuclear power plants work because of fission reactions.  While there are types of nuclear reactors all over the universe, the first man made one was created only 50 years ago.

Fig 10

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