Chemistry - Lise Meitner and nuclear fission
Lise Meitner and nuclear fission
Chadwick's discovery of the neutron, opened new avenues of research into
reactions. The fact that neutrons had no charge encouraged their use in
bombarding the nuclei of atoms. The idea was that if the nucleus of an atom
of a particular element could absorb an extra neutron, then a different
isotope of that element should be produced.
Neutron bombardment of uranium was also considered to be a way of
producing elements heavier than uranium - the transuranium elements.
Otto Hahn, Fritz Strassmann and Lise Meitner worked together on the
neutron bombardment of uranium in Germany in the 1930s. Eventually Meitner,
being Jewish, had to flee Germany and went to work with Bohr.
Hahn and Strassmann continued to work on the neutron bombardment of
uranium (atomic number 92) and were stunned to discover barium (atomic
number 56) as a product of this bombardment.
Within weeks, it was discovered that were also during the fission of
uranium and that these neutrons could cause the splitting of more uranium
nuclei and lead to a
The first step in the fission of uranium-235 involves the formation of
unstable U-236 nuclei by bombardment with neutrons.
Each unstable U-236 nucleus breaks down into a Kr-92 nucleus and a Ba-141
nucleus accompanied by the release of three neutrons.
Nuclear fission can take place spontaneously or it can be induced by such
as neutrons, protons or alpha particles or with electromagnetic radiation
in the form of gamma rays. It occurs most readily with heavy elements such
as uranium and plutonium. The two nuclei formed as a result of this
bombardment are both positively charged and repel each other.
The fission of one kilogram of uranium releases as much energy as is
obtained from burning approximately 3 000 tonnes of coal.
It was mentioned earlier that, as well as new nuclei, several neutrons are
formed from the fission of uranium. These neutrons can strike other uranium
nuclei, which then release more neutrons. The extra neutrons can then split
further uranium nuclei, and so the process goes on and can be
self-sustaining in what is known as a Then destructive power of such a
fission reaction was exploited in the atomic bombs used to end the Second
World War. Today we see constructive applications in nuclear reactors,
which effectively harness the fission process for electricity generation.
Nuclear fission is the basis of all existing nuclear power stations.
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