Fission

Fission


The atom has three particles

     
  • Protons are positively charged and reside in the nucleus (blue balls)
  • Neutrons have no electrical charge and also reside in the nucleus (yellow balls)
  • Electrons have a negative charge and are bound to the atom outside of the nucleus

 

 

Due to the electrically charged electron cloud on the outside of the atom it is very difficult to smash other particles into the nucleus. Only a particle with no electrical charge can easily reach the nucleus. In 1932 Chadwick (pictured at left) discovers the neutron which has no charge.

 

 

In December of 1938 Otto Hahn, Lise Meitner, and Frederick Strassmann split U-235 atoms by bombarding them with neutrons. These extra neutrons cause the nucleii to become unstable which causes fission.

 

This is the equation for the fission reaction that they saw

 

Each Uranium 235 atom needs a neutron to split. After it splits, each atom gives off three neutrons. This means that each atom that splits can split three more atoms. This can keep going causing a chain reaction.

This is a simulated picture with only two neutrons coming out.

There are two types of chain reactions. One is called controlled the other uncontrolled.

This is an example of uncontrolled chain reaction


It is quickly realized that the products of these reactions weigh less than the reactants. This means that a fission reaction will produce a large amount of energy according to Einstein's equation E=mc2. Hear Einstein explain this equation in his own words.

If the products of a nuclear reaction weigh less than the reactants, this means that the mass did not simply disapear, but was converted into energy. A tiny little mass difference amounts to a large amount of energy because c2 in Einstein's equation is equal to 9000000000000000000 m2/s2.


This means that we can use fission to produce electricity (through a controlled chain reaction), or make an explosion (through an uncontrolled chain reaction).

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