# Nuclear Binding Energy (wikipedia is confusing)

1. Jan 20, 2013

### hms.tech

http://en.wikipedia.org/wiki/Nuclear_binding_energy

What is nuclear binding energy ?

Here are two possible answers according to the Wikipedia page :
1.Nuclear binding energy is the energy required to split a nucleus of an atom into its component parts.
2.Nuclei are made up of protons and neutron, but the mass of a nucleus is always less than the sum of the individual masses of the protons and neutrons which constitute it. The difference is a measure of the nuclear binding energy which holds the nucleus together.

Which one is it ?
Or
are both of them trying to tell the same thing ?

2. Jan 20, 2013

### Studiot

3. Jan 20, 2013

### VantagePoint72

They are the same thing. The energy of a nucleus is less than the total energy of the individual nucleons, since the bound nucleus has lower potential energy. This energy difference is measurable as a difference in rest mass via $E=mc^2$. If you want to split the nucleus apart, you need to add in enough energy to make up the difference.

4. Jan 20, 2013

### hms.tech

Am I correct in thinking that this lowering of potential energy is caused by the strong nuclear force between any two nucleons ?

5. Jan 20, 2013

### Staff: Mentor

The (repulsive) electrical force also contributes to the binding energy. The binding energy is smaller than it would be if the nuclear force were the only one acting. This is what makes very heavy nuclei unstable: the electrical repulsion eventually overcomes the attraction of the nuclear force, when the number of protons is large enough.

6. Jan 20, 2013

### VantagePoint72

It would probably be less confusing to phrase that as, "The (repulsive) electrical force also detracts from the binding energy."

7. Jan 20, 2013

### Staff: Mentor

Correction accepted.

I tend to think of "contribute" as being either positive or negative, but I can see this might be confusing.

8. Jan 20, 2013

### hms.tech

I understand, thank you

In summary both definitions are correct , its just that this one
Nuclear binding energy is the energy required to split a nucleus of an atom into its component parts.

is more modern (new)