Please explain binding energy?

[alexgmcm]

Can some kind person please explain why He-4 is so high and Li-6 is so low on the graph of binding energy per nucleon.
Copy of the graph here http://en.wikipedia.org/wiki/File:Binding_energy_curve_-_common_isotopes.svg"
It means that He-4 must be very stable right? Because binding energy is indicative of stability for reasons I can't quite recall at the moment.. but why is there such a spike as it goes up to He-4 and then down to Li-6 and Li-7 etc.

I remember in something about astrophysics it said there were like resonances in C-12 for example that made it more stable than one might expect so is that the case for He-4? But otherwise why is it so stable, or is Lithium just very unstable?

Argh, this stuff gets pretty confusing.. any help would be greatly appreciated.

 

[malawi_glenn]

Yes He-4 is very stable.

But explaning WHY He-4 is high and WHY Li-6 low BE/nucleon is that He-4 has closed proton- and neutron shells.

http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/shell.html

http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/shell2.html#c4

The nuclei which has filled shells have significant higher BE/nucleon that its neigbours, this is a consequence of quantum physics really, you have the same thing in atoms with their electron shells.

 

[sir-pinski]

Binding energy refers to the amount of energy required to break apart a nucleus into its individual nucleons (protons and neutrons). It is a measure of the strength of the nuclear force that holds the nucleus together.

In the graph of binding energy per nucleon, you can see that as you move towards heavier elements (towards the right on the graph), the binding energy per nucleon increases. This is because as the number of nucleons increases, the strong nuclear force has more particles to act on, resulting in a stronger binding energy.

Now, let's focus on He-4 and Li-6 specifically. He-4 has a very high binding energy per nucleon, meaning it takes a lot of energy to break apart this nucleus. This is because He-4 is a very stable isotope. It has a perfect balance of protons and neutrons, with 2 protons and 2 neutrons, giving it a very stable nuclear configuration. This is also why He-4 is commonly used in nuclear reactions, such as in nuclear power plants.

On the other hand, Li-6 has a relatively low binding energy per nucleon compared to He-4. This is because Li-6 is not as stable as He-4. It has 3 protons and 3 neutrons, which is not a perfect balance, making it less stable. This is also why Li-6 is not commonly used in nuclear reactions.

As for the spike in the graph, this is due to the phenomenon of nuclear resonances. In certain nuclei, there are specific energy levels at which the nucleus becomes more stable due to the alignment of protons and neutrons. This results in a higher binding energy at these specific energy levels, creating spikes on the graph.

In summary, He-4 is so high on the graph of binding energy per nucleon because it is a very stable isotope, with a perfect balance of protons and neutrons. Li-6 is relatively low on the graph because it is not as stable, with an imbalance of protons and neutrons. The spike in the graph is due to nuclear resonances, which result in higher binding energy at specific energy levels.