Question

Assertion :The binding energy per nucleon, for nuclei with the atomic mass number $A>100$, decreases with $A$. Reason: The nuclear forces are weak for heavier nuclei.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

Answer: (A)

Binding energy per nucleon decreases with A for nuclei with the atomic mass number $A>100$ due to weak nuclear forces. It can. be explain as :
At short distances, the nuclear force is stronger than the Coulomb force; it can overcome the Coulomb repulsion of protons inside the nucleus. At typical nucleon separation $\left(1.3fm\right)$ it is a very strong attractive force $\left(104newtons\right)$. Beyond about $1.3fm$ separation, the force exponentially dies off to zero. However, the Coulomb force between protons has a much larger range and becomes the only significant force between protons when their separation exceeds about $(2.5fm,A>100)$.