We are asked about the difference between the atomic mass and mass of the nucleus of iron-56 (56Fe)
• Recall that the nucleus consists of protons and neutrons.
• A nucleon is either a proton or neutron. Thus, the mass of individual nucleons is the sum of the masses of protons and neutrons.
Mass of individual nucleons = Mass of protons + Mass of neutrons
Table Mass Defects and Binding Energies for Three Nuclei
|Nucleus||Mass of Nucleus (amu)||Mass of Individual Nucleons (amu)||Mass Defect (amu)||Binding Energy (J)||Binding Energy per Nucleon (J)|
|24 He||4.00150||4.03188||0.03038||4.53 10-12||1.13 10-12|
|2656 Fe||55.92068||56.44914||0.52846||7.90 10-11||1.41 10-12|
|92238 U||238.00031||239.93451||1.93420||2.89 10-10||1.21 10-12|
The atomic mass of iron-56 is 55.93494 amu.
Why is this number different from the mass of the nucleus given in the table above?