JAMES CHADWICK AND THE NEUTRON BY: ALANA NOEHRENBERG & ALEXA JOHNSON

BIOGRAPHY OF JAMES CHADWICK James Chadwick was born on October 20th, 1891 He was born in Manchester, United Kingdom He died on July 24th, 1974 He died in Cambridge, United Kingdom

PLACES WHERE MOST SIGNIFICANT WORK WAS DONE James Chadwick, while working under Ernest Rutherford at Cambridge in 1932, proved the existence of neutrons What are neutrons? Neutrons are elementary particles without any electrical charge and are a fundamental building block of the atom's nucleus Another significant place where Chadwick worked was America, where he contributed to the Manhattan Project which developed the world's first atomic weapons Chadwick’s last major work before leaving Cambridge for Liverpool was with his personal assistant, Maurice Goldhaber  Using a suggestion of Goldhaber’s, they demonstrated the nuclear photoelectric effect in the form of the disintegration of deuterium under gamma ray illumination  In other words, they found the first accurate figure of the mass of the neutron

CHADWICK’S COLLEAGUES & RIVALS Some of Chadwick’s colleagues were Ernest Rutherford, Hans Geiger, Ernest Marsden, Charles Darwin, and Henry G. J. Moseley, and Niels Bohr A rival of Chadwick’s was Ernest Rutherford, yes, Rutherford was colleague turned rival  This was due to the fact that in the early 1930’s the development of nuclear physics caused dispute  Chadwick believed that a new invention called the cyclotron particle accelerator would rapidly become an essential tool for his research  Chadwick wanted one at Cambridge, however, Rutherford refused to have one Ernest Rutherford Cyclotron Particle Accelerator

THOMSON’S DISCOVERY OF THE ISOTOPES OF NEON Chadwick didn’t just guess that there was a new kind of particle to be found It was Thompson’s discovery that neon was composed of two different kinds of atoms, proving the existence of isotopes in a stable element, which sparked Chadwick’s curiosity After Thomson’s studies Chadwick knew there was an unknown particle yet to be discovered, and that he was going to find it J.J Thomson

THE DISCOVERY OF THE NEUTRON James Chadwick discovered the neutron in 1932 He performed experiments with the goal of looking for a neutral particle- one with the same mass as a proton, but with zero charge He used scattering data to calculate the mass of a neutral particle He bombarded beryllium atoms with alpha particles which produced an unknown radiation Chadwick interpreted this radiation as being composed of particles with a neutral electrical charge and the approximate mass of a proton This particle became known as the NEUTRON!!! He was able to determine that the neutron DID exist and that its mass was about 0.1 percent more than the proton’s

HARDSHIPS AND SIGNIFICANCE The neutron was so hard to detect because it was uncharged  There was no electrical repulsion of the neutron when it passed through matter, so it was be much more penetrating than the proton  Adding to the confusion at the time was the fact that neutrons are not stable The significance of the discovery of the neutron was that:  It dramatically changed the picture of the atom  It accelerated discoveries in atomic physics

CHADWICK’S PART IN THE DEVELOPMENT OF ATOMIC THEORY With the discovery of the neutron, an adequate model of the atom finally became available to chemists Since 1932, through continued experimentation, many additional particles have been discovered in the atom Also, new elements have been created by bombarding existing nuclei with various subatomic particles The atomic theory has been further enhanced by the concept that protons and neutrons are made of even smaller units called quarks Thanks Chadwick!!!

FUN FACTS Chadwick had twin daughters named Joanna Stewart Chadwick Batterham and Judith Chadwick Chadwick was taken prisoner at Zivilgefangenenlager, Ruhleben, a concentration camp during World War I

WORK CITED Great Physicists by William H. Cropper