- 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 [14]
Define binding energy per nucleon.
Binding energy per nucleon is the least amount of energy required to liberate all of the nucleons from the nucleus.
As a result, the binding energy per nucleon is
`E_B/A`
Define unified atomic mass unit.
`1/12`th of the mass of an atom of 6C12 isotope.
With reference to Nuclear Physics, answer the following question.
Define lu (where u stands for unified atomic mass unit).
1 AMU is the average of proton rest mass and the neutron rest mass. Thus can be expressed as
1 AMU = 1.67377 × 10-27 kg
= 1.67377 × 10-24 gram
and C-12 is considered a reference for all atomic mass calculations.
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.
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 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 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.
Define one Becquerel.
One Becquerel (Bq) is defined as the activity of a quantity of radioactive samples in which one nucleus decays per second. It is the SI unit of the activity.
Definition: Nuclear Energy
The energy released due to loss in mass during the processes of nuclear fission and fusion is called nuclear (or atomic) energy.
OR
The energy released when nuclei undergo a nuclear reaction (change in structure, forming new nuclei) is called nuclear energy.
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.
Definition: Mass Number
The mass number of an atom is equal to the total number of nucleons (i.e., the sum of the number of protons and the number of neutrons) in its nucleus.
Define the term atomic number.
The number of protons in the nucleus is known as the atomic number of the element and is denoted by Z.
Define the term mass number.
The total number of neutrons and protons in the nucleus is called the mass number of the element and is denoted by A.
Definition: Atomic Number
The atomic number of an atom is equal to the number of protons in its nucleus (which is same as the number of electrons in a neutral atom).
Key Points
Key Points: Nuclear Fission
Key Points: Structure of the Atom and Nucleus
- The structure of an atom and its nucleus was developed from the discovery of electrons by J.J. Thomson and alpha particle scattering experiments by Rutherford.
- An atom consists of electrons, protons, and neutrons, with protons and neutrons in the nucleus and electrons revolving in stationary orbits.
- The maximum number of electrons in a shell is given by 2n², and the shells are named K, L, M, N, O, P, and Q.
Concepts [27]
- Introduction of Atoms
- Alpha-particle Scattering and Rutherford’s Nuclear Model of Atom
- Atomic Spectra
- Bohr’s Model for Hydrogen Atom
- Energy Levels
- The Line Spectra of the Hydrogen Atom
- De Broglie’s Explanation of Bohr’s Second Postulate of Quantisation
- Hydrogen Spectrum
- Atomic Masses and Composition of Nucleus
- Size of the Nucleus
- Mass-energy and Nuclear Binding Energy
- Mass - Energy
- Nuclear Binding Energy
- Atomic Mass, Mass - Energy Relation and Mass Defect
- Nuclear Force
- Radioactivity
- Law of Radioactive Decay
- Alpha Decay
- Beta Decay
- Gamma Decay
- Forms of Energy > Nuclear Energy
- Nuclear Fission
- Nuclear Reactor
- Nuclear Fusion – Energy Generation in Stars
- Controlled Thermonuclear Fusion
- Structure of the Atom and Nucleus
- Mass-Energy Equivalence and Nuclear Reactions
