Problem: Table Mass Defects and Binding Energies for Three NucleiNucleusMass of Nucleus (amu)Mass of Individual Nucleons (amu)Mass Defect (amu)Binding Energy (J)Binding Energy per Nucleon (J)24 He 4.001504.031880.030384.53 10-121.13 10-122656 Fe55.9206856.449140.528467.90 10-111.41 10-1292238 U238.00031239.934511.934202.89 10-101.21 10-12The 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?

FREE Expert Solution

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


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Problem Details

Table Mass Defects and Binding Energies for Three Nuclei


NucleusMass of Nucleus (amu)Mass of Individual Nucleons (amu)Mass Defect (amu)Binding Energy (J)Binding Energy per Nucleon (J)
24 He 4.001504.031880.030384.53 10-121.13 10-12
2656 Fe55.9206856.449140.528467.90 10-111.41 10-12
92238 U238.00031239.934511.934202.89 10-101.21 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?