- In nuclear fission of U‑235, a slow neutron is absorbed to form unstable U‑236, which splits into two nuclei with the release of three neutrons and energy.
- Energy released in fission is due to loss of mass, and is given by Einstein’s mass‑energy relation, E = (Δm)c2.
- In each fission reaction, atomic number (Z) and mass number (A) remain conserved, though mass is converted into energy.
- Fission of one U‑235 nucleus releases nearly 190 MeV energy, mainly as kinetic energy of fragments, neutrons, γ‑rays, heat, and light.
Definitions [10]
Define impact parameter.
The impact parameter is defined as the perpendicular distance between the centre of the gold nucleus and the direction of the velocity vector of the alpha particle when it is at a large distance.
Define atomic mass unit u.
One atomic mass unit (u) is defined as the 1/12th of the mass of the isotope of carbon \[\ce{^12_6C}\].
Define the ionization energy.
The minimum energy required to remove an electron from an atom in the ground state is known as binding energy or ionization energy.
Define the ionization potential.
Ionization potential is defined as ionization energy per unit charge.
Definition: Isotopes
The atoms of the same element, having same atomic number Z, but different mass number A, are called isotopes.
OR
Atoms having the same atomic number (Z) but different mass numbers (A).
Define bound electrons.
As nucleus is positively charged it strongly attracts the negative charged electrons. The electron orbit close to the nucleus are tightly bound by strong attractive force of nucleus. These electrons are known as bound electrons.
Define free electrons.
Electrons in outer orbits are weakly bound with the nucleus. In solids these weakly bound electrons leave their individual atom and become a part of it. These electrons are known as free electrons.
Define the term radioactivity.
The phenomenon of spontaneous disintegration of an unstable nucleus of a naturally occurring isotope accompanied by emission of active radiations, α particles, β particles and γ radiations is called radioactivity.
Definition: Radioactivity
Radioactivity is a nuclear phenomenon. It is the process of spontaneous emission of α or β and γ radiations from the nucleus of atoms during their decay.
Definition: Nuclear Fission
Nuclear fission is the process in which a heavy nucleus splits into two lighter nuclei of nearly the same size, when bombarded with slow neutrons. In each fission reaction, a tremendous amount of energy (≈ 190 MeV) is released.
Key Points
Key Points: Nuclear Fission
Concepts [13]
- Introduction to Atomic and Nuclear Physics
- Electric Discharge Through Gases
- Introduction to Atom Models
- Nuclei
- Constituents of a Nucleus
- Isotopes
- Atomic and Nuclear Masses
- Size and Density of the Nucleus
- Mass Defect and Binding Energy
- Nuclear Force
- Radioactivity
- Nuclear Fission
- Nuclear Fusion – Energy Generation in Stars
