Question

Define 'Mass defect' and 'Binding energy' of a nucleus. Describe 'Fission process' on the basis of binding energy per nucleon.

Hint:

The fission process is driven by the increase in binding energy per nucleon as large nuclei split into smaller ones, releasing energy.

Answer 1

Nuclear Mass Defect, Binding Energy, and Fission

1. Mass Defect

The mass defect of a nucleus represents the disparity between the combined mass of its individual protons and neutrons and the nucleus's actual measured mass. It is calculated as:

\[ \Delta m = \text{Total nucleon mass} - \text{Nucleus mass} \]

2. Binding Energy

Binding energy is the energy required to disassemble a nucleus into its constituent protons and neutrons. This energy is directly proportional to the mass defect, as described by Einstein's equation:

\[ E = \Delta m c^2 \]

Here, \( \Delta m \) signifies the mass defect, \( c \) is the speed of light, and \( E \) represents the binding energy.

3. Fission Process

Nuclear fission describes the fragmentation of a heavy nucleus, such as uranium-235, into two or more lighter nuclei, accompanied by a significant energy release. This process is initiated when a nucleus captures a neutron, rendering it unstable. During fission:

• The nucleus divides into smaller fragments.
• A substantial amount of energy is liberated due to a higher binding energy per nucleon in the resulting fission products.
• The increase in binding energy per nucleon upon nuclear splitting leads to energy emission.