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Chadwick and the Neutron

By: Sophie Greenbaum and Ariel Silverman

James Chadwick

• Sir James Chadwick was born on October 20, 1891 in Bollington, Cheshire, England

• He was the first child of John Joseph and Anne Mary Knowles Chadwick

• He graduated from University of Manchester

• Married in 1925 with twin girls

James Chadwick

James Chadwick Education

• English physicist• After graduating, he was Rutherford’s

coworker who took him to the Cavendish Laboratory at the University of Cambridge where he received his Doctor of Philosophy degree

James Chadwick Achievements

• Head of the British scientists who worked on the Manhattan Project during World War II

• Knighted in 1945 for his accomplishments and achievements in Physics

• He worked on many radio activity problems

• He gained his M. S. C (Master of Science) degree in 1913

The Connection of Thomson and Chadwick’s Discoveries

• Thompson discovered neon isotopes• Chadwick discovered the neutron• Thompson determined the ratio of the charge to

mass e/m of the electron and that cathode rays consist of discrete particles of matter

• Isotopes are different types of atoms of the same chemical element which each have a different number of neutrons

• The neutrons explain the differences in weight J.J. Thomson

The Discovery

• Chadwick discovered the neutron in 1932• He noticed a inconsistency between the

atomic numbers of atoms and the atomic weight

• When they were studying atomic disintegration when they kept noticing that the atomic number was less than the atomic mass

The Discovery• Chadwick came to the idea that there were two

extra particles in a Helium atom• There were numerous reports of particles that

turned out to be incorrect, many of Chadwick’s peers didn’t agree to his neutral particle theory

• They assumed that the particles were actually Gamma rays (neutral, high energy photons)

• Chadwick then went out and tried to prove that the neutral radiation had mass

• The neutral radiation needed to have the same masses

The Discovery• Chadwick put a piece of beryllium in a vacuum

chamber with some polonium • The polonium set out alpha rays which struck the

beryllium and they gave out neutral rays • He put a target in the path of the rays and when they

hit the target they knocked atoms out of it• These atoms became electrically charged and they flew

into a detector filled with gas • Passing through the chamber, it ionized the gas

molecules and it drifted toward an electrode • The explanation for all his results was a neutral

particle which is the neutron

The Neutron

• Subatomic particles that have n or n0 symbol• No electric charge and its mass is a little bit more

than a protons • Necessary within an atomic nucleus • Discovered in 1932• In 1932,Chadwick it might cause a nuclear chain

reaction• The main role of the neutrons in the nucleus of an

atom is to add to the binding energy that holds the nucleus together

• In order to overcome the forces of the protons, neutrons are included in the structure

Chadwick’s Part in the Development of the Atomic Theory

• James Chadwick contributed to atomic theory by his experiments and observations proving and discovering the neutron

• He won the Nobel Prize in 1935 for this discovery

WORKS CITED:

- http://www.nature.com/physics/looking-back/chadwick/index.html

- http://www.pbs.org/wgbh/aso/databank/entries/dp32ne.html

- http://www.biography.com/people/jj-thomson-40039

- http://www.famousscientists.org/james-chadwick/