Question

Two nuclei: A and B have very similar binding energy per nucleon. This means that on breaking into smaller nuclei:

• A. Both will release energy
• B. Both will absorb energy
• C. They will release or absorb energy based on their atomic number (or number of nucleons)
• D. How am I to predict this, am I supposed to be an astrologer?

Answer 1

The correct option is C They will release or absorb energy based on their atomic number (or number of nucleons)

Take a deep breath and look at the graph:

Now, consider, say, Oxygen and Uranium nuclei. They have very similar binding energy per nucleon.

But, does that mean they are equally happy breaking into smaller nuclei? Or, to be more ‘physics’ally (not a word) correct, does it mean both will release energy if they break into smaller nuclei?

The answer is no; because any nuclei smaller than U might have a higher binding energy per nucleon than U itself, it might release energy on breaking into them.

However, nuclei smaller than O all have lower binding energy per nucleon than O itself which means that O will absorb energy in breaking down. So, we can safely conclude that the release or absorption of energy depends on the atomic number (number of nucleons).