How to explain the mass deffect?

[mahela007]

I understand that when , say, several protons and neutron come together to from a nucleus they loose some mass and that this mass is lost as ENERGY as proven by Einstein. But does that actually mean that the protons and neutrons become a bit lighter? And is this what accounts for the mass defect (i.e why the relative atomic mass of any atom except C12 is not a whole number)?

 

[fatra2]

Hi there,

You are exactly right. The protons and neutrons, in an atomic nucleus become a bit lighter. This also explains your example with the C12 atom and many other.

By the way, as long as the nucleus is whole, the protons ans neutrons will be a little lighter. This mass defect is transformed into binding energy (energy that glues them together). This energy is the effect of the strong nuclear interaction.

Cheers

 

[sir-pinski]

The mass defect is a phenomenon that occurs when protons and neutrons come together to form a nucleus. As you mentioned, this process results in the loss of some mass, which is then converted into energy, as described by Einstein's famous equation E=mc^2. This energy is released in the form of electromagnetic radiation, such as gamma rays.

To answer your question, yes, the protons and neutrons do become slightly lighter when they form a nucleus. This is because the binding energy that holds the nucleus together is actually a form of potential energy, and according to the law of conservation of energy, this energy must come from somewhere. In this case, it comes from the mass of the individual protons and neutrons, resulting in a decrease in their overall mass.

This mass defect is responsible for the difference between the actual mass of an atom and its mass number, which is the sum of its protons and neutrons. This is why the relative atomic mass of any atom (except carbon-12) is not a whole number - because it takes into account the mass defect.

It's important to note that the mass defect is a very small amount, as the vast majority of an atom's mass comes from the protons and neutrons themselves. However, this small difference is crucial in understanding the stability of atoms and the energy released in nuclear reactions.

Overall, the mass defect is a fundamental concept in nuclear physics and plays a crucial role in our understanding of the behavior of atoms and the universe as a whole.