Question

The average binding energy per nucleon is maximum for the nucleus :

• A. ${{}_{2}He}^4$
• B. ${{}_{8}O}^{16}$
• C. ${{}_{26}Fe}^{56}$
• D. ${{}_{92}U}^{238}$

Answer 1

Answer: (C)

${{}_{26}Fe}^{56}$

The average binding energy per nucleon is maximum for the nucleus ${{}_{26}Fe}^{56}$.
${{}_{26}Fe}^{56}$ is the most efficiently bound nucleus. It has the least average mass per nucleon.
The net binding energy of a nucleus is the difference between the nuclear attraction and the electrostatic repulsion between positively charged protons. With increase in atomic number from helium, their net binding energy per nucleon slowly grows, reaches its peak at iron and then decreases.
As more and more nucleons are added, the total nuclear binding energy increases, but proton-proton repulsion also increases, and past iron, the second increase outweighs the first.