Living Wax Museum
James Chadwick
Biography
James Chadwick was detained as a civilian prisoner of war for four years WW1. He then got a scholarship to study in Germany, he actually entered the physics program by mistake! He happened to be waiting in the wrong registration are when he intentionally wanted mathematics. At the low age of 21 he had already published 5 scientific papers. His research focused on radioactivity. He became a nuclear physician thus creating the existence of a Neuron .His discovery with Rutherford and his help they dramatically changed the image of the atom and quickened the discovery in atomic physics. He found that electrons are emitted in a continuous spectrum, at odds with other group’s results, and a finding that eventually led to the theory and discovery of the neutron. By the conservation of momentum and energy he was able to determine that the neutron had a mass slightly greater than the proton.
Leading up to the Experiment
One of chadwicks first tasks was working with Rutherford to establish a unit of measurement for radioactivity. Chadwick developed a method in which flashes called scintillations in zinc sulfide crystals were observed in total darkness using a microscope. Although it was prone to error, later detection confirmed Chadwick's measurements.
Rutherford and Chadwick also spent much time experimenting with the transmutation of elements. They attempted to break up the nucleus of an element so that other elements formed. To do so, these experiments included the bombarding the nuclei of nitrogen and other helium nuclei elements. This eventually led to other experiments to determine the size and structure of the atomic nucleus. For several years Chadwick and Rutherford struggled with an inconsistency when transmutating elements. Nearly every element had an atomic number less than that of its atomic mass. Something besides the protons in the nucleus had to add to the mass.
For example, a helium atom has an atomic mass of 4, however it’s atomic number is only 2.
Experimental Design
Rutherford came up with an idea that there may actually be a particle with mass but no charge. He called it a neutron, and imagined it paired with electrons and protons. Chadwick kept this in mind while he conducted his experiments trying to find the neutron. Chadwick conducted similar particle radiation experiments as before, with the new goal of finding a neutral particle.
Chadwick bombarded boron with alpha particles that emitted neutral rays. And placed a hydrogen target in the ray’s path. Once the ray hit the target protons flew out. He then measured the velocity of the protons and using the laws of conservation of momentum energy. Chadwick calculated the mass of the neutron which was roughly 0.1% greater than the protons.
He found it!
Overall Contribution to The change of the Atom
Development of a new Atomic Model
Chadwick was credited for the discovery of the neutron. Chadwick worked alongside Rutherford whilst struggling with inconsistency, noticing how every element had an atomic number less than it’s atomic mass. Rutherford proposed that possibly a neutral particle could be found within the atom- yet they could not prove this. Eventually, through the experimentation of beryllium becoming radioactive after being exposed to alpha particles (Joliot-Curies), Chadwick found his answer. By filling a cloud chamber with nitrogen, Chadwick showed that the radiation caused the nitrogen atoms to recoil. The energy in the recoiling could only be caused by collisions with uncharged particles having around the same mass as protons- proving the existence of the neutron.
Get to Know Chadwick.
-Spent two years under professor Ernest Rutherford, studying radioactivity problems.
-Extremely intelligent, received several scholarships, and even studied in Germany.
-Worked on the Manhattan Project.