Atomic Mass Units: Discrepancy Explained?

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SUMMARY

The discussion centers on the discrepancy between the defined mass of a carbon-12 atom (12 amu) and the sum of the individual masses of its constituent protons (1.007 amu each) and neutrons (1.009 amu each). The key conclusion is that the difference arises from the binding energy of the carbon-12 nucleus, which accounts for the mass defect due to the strong nuclear force. This binding energy is a result of the energy required to hold the protons and neutrons together, which is not reflected in their individual masses when they are isolated.

PREREQUISITES
  • Understanding of atomic structure and subatomic particles
  • Familiarity with the concept of atomic mass units (amu)
  • Knowledge of binding energy and its implications in nuclear physics
  • Basic principles of relativity as they pertain to mass-energy equivalence
NEXT STEPS
  • Research the concept of binding energy in nuclear physics
  • Study the mass-energy equivalence principle as described by Einstein's theory of relativity
  • Explore the differences between isolated particles and particles within atomic nuclei
  • Learn about the strong nuclear force and its role in atomic stability
USEFUL FOR

Students of chemistry and physics, educators teaching atomic theory, and anyone interested in understanding the principles of nuclear binding and mass discrepancies in atomic structures.

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Been many years since I took general and org chem and am currently reading general chem textbook as refresher. Came across definition of amu (atomic mass unit). Text says that the mass of the carbon-12 atom is defined to be exactly 12 amu. However, a couple of pages over, I read that the mass of the proton is about 1.007 amu, and the mass of the neutron is about 1.009 amu. Add up the masses of 6 protons and 6 neutrons for the carbon-12 atom, and you come up with more than 12 amu. I can't resolve this apparent discrepancy. I've consulted other texts, etc. Does some type of relativistic effect bear on this situation? In other words, does, for example, an isolated proton have a mass of 1.007 amu, but then when part of an atom have a slightly different mass because of some relativistic effect? HELP!
 
Chemistry news on Phys.org
The mass difference is the "binding energy" for 12C.
 

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