physics-subatomic-particles

were what was happening, as the mass defect of ti3 C is about 10 7 eV, and that of 5 B earound zero, a particle of energy about 1 .4 x 10 7 eV would be produced . The mass defec tof a given isotope is the difference between its actual mass and its predicted mass ,that is, its atomic number times the average mass of the proton and neutron. The nuclearreaction in question would be written as follows : 9 Be-ece. + particle . The theoreticalenergy of the particle if this reaction were taking place was approximately in agreemen twith experimental values, and so it was assumed that this was the reaction taking place .ehadwick found in 193? that this new particle also ejected particles from many otherlight elements apart from hydrogen .It was Chadwick who continued the research into this type of radiation, and h edecided, assuming the validity of the law of the conservation of energy and momentum ,that the new particle must have a mass near that of the proton . This being so, h esuggested that the newly discovered particle was the neutron predicted by Rutherfor dsome twelve years before . Feather and Chadwick determined the approximate mass of theneutron as follows : inside a vacuum chamber, alpha particles from a sample of poloniu mwere made to hit beryllium foil, thus producing neutrons . These neutrons travelle dout through a window in the vacuum chamber until they reached some paraffin (CH L ) orparacyanogen (CN) from which they ejected protons which were then counted by means o fa proportional counter (see chapter 8) . By careful integration of the results obtainedwith paraffin slabs and those with paracyanogen ones, a value of 1 .006 proton masse swas deduced for the mass of the neutron . Chadwick believed that this mass, just slightl yless than than the sum of the masses of the proton_and the electron, represented abound state of these two particles . The fact that the subsequent mass was less than th esum of its component parts, he explained as being caused by the bonding energy necessar yto hold the two constituent particles together . However, it can be shown, using moderntechniques, that it is impossible to achieve this bound state without using an energyfar in excess of the mass of the electron . Thus the atomic nucleus came to be considere das a system containing two types of particles : protons and neutrons, which soon becam econsidered by most physicists as particles in their own right .