Mass+Defect

During a nuclear reaction, energy is lost to surroundings or to teh creation of a new particle. This missing energy is known as the mass defect, which is not to be confused with the video game Mass Effect. The mass defect can be found using the formula: D // m // = //m//parent - //m//products Where: Delta m= Mass Defect m parent= mass of parent element m products= mass of products

The mass is usually not measured in kg however, as it is a bad way to measure small particles. Instead the atomic mass unit, u, is used. 1 u= 1.660539x10^-27 kg 1 u= 1.49x10^-10 J  1 u= 931.4941 MeV

Mass defects are converted to energies using the infamous E=mc^2 formula where: E= energy in J or MeV m= mass defect in J or MeV c= the speed of light 3x10^8 or 2.997925x10^8 m/s

= Mass Defect and Binding Energy Between Nucleons in Atoms =

For questions that ask you to find the binding energy in single atoms not undergoing nuclear deacy, the masses of protons and neutrons are needed: Proton: 1.007825 u Neutron: 1.008665 u  Pages 794-796 in the Pearson textbook have questions on this topic

=Alpha Decay= During Alpha decay, a parent isotope decays into a daughter and alpha particle. Assuming the parent starts at rest, the binding energy released is transferred to the energy in the alpha particle, through the conservation of energy. Eamples of this topic are on page 801 in the Pearson textbook

=Beta Decay= During a beta negative decay, a neutron is converted to a proton, electron (beta negative particle) and an antineutrino. Beta positive decay is the decay of a proton into a into a neutron, positron (Beta positive particle) and a neutrino. The calculations for mass defect in Beta decay are very similar to the ones used in alpha decay. The masses of beta particles or neutrinos/antineutrinos are not used in these calculations. Page 810 in the Pearson textbook has questions on this topic.

=Nuclear Fission= In nuclear fission, an unstable nucleus breaks apart creating a large amount of energy. Finding the difference in mass between the product and reactants will give mass defect. Example on page 819 in the Pearson textbook.

For more information on Alpha Decay, and Beta Decay please see Alpha Decay and Decay Types For more information see Mr. Langdale's handout "Mass Defect and Binding Energies Revisited" For more information on Nuclear Fission please see Nuclear Fission For more Practice Questions address the Pearson Physics textbook References 1. P30 Unit D: Mass Defect and Binding Energies Revisted