Question

If two protons and two neutrons are brought extremely close together to form a single, bound particle, the energy released in the process will be equal to:

• A. The binding energy of helium nucleus
• B. There will be no energy released
• C. There might or might not be any energy released
• D. The mass-energy of an alpha particle.

Answer 1

The correct option is A The binding energy of helium nucleus

Binding energy, by definition, is the amount of work you need to do to separate nucleons bound in a nucleus to infinity. Since (for most nuclei), you need to supplyenergy to free the nucleons, the opposite process will release energy - bringing nucleons together to form a nucleus will release energy.

This is exactly what we are doing here. Bringing two protons and two neutrons together to form a nucleus - but of what element? ${}_2^{4}He$ , or helium-4. Right?
The amount of energy released in this process = the energy you need to supply to a ${}_2^{4}He$ nucleus to completely disassemble it = binding energy of helium-4.