Nuclear Reactions

Nuclear Reactions:

  • Reaction in which there is a change in the composition of the nucleus is called nuclear reaction.
  • In nuclear reaction rearrangement of nucleons ( constituents of nucleus) takes place and thus the composition of nucleus changes
  • In nuclear reaction sum of atomic mass numbers and sum of atomic numbers of reactant nuclei, should be equal to that of product nuclei.
  • The rate of nuclear reaction is independent of temperature.
  • In a nuclear reaction, the energy values are given in MeV per nucleus transformed.

Chemical reaction:

  • Reaction in which there is change in chemical composition of reacting substances is called chemical reaction.
  • In chemical reaction redistribution of electrons and rearrangement of atoms takes place
  • The total number of atoms of each element must be same on both the sides of chemical equation.
  • Rate of chemical reaction depends on temperature.
  • In chemical reaction heat of reactions are given in kJ per mole.

Nuclear Reactions:

Artificial Transmutation:

  • The process of conversion of a nucleus of atom one element into that of another element by using high-velocity projectiles is called as artificial transmutation.The new element form may or may not be radioactive.

Nuclear Reactions 01

  • Target: The nucleus of an atom which is bombarded by high-speed particles is known as the target.
  • Projectile: A high speed (accelerated) particles which strike nucleus of an atom (target) to carry out artificial transmutation is called projectile. Projectiles used are  1H1 (proton), 2He4 (α -particles), -1 e0( β – particles),  on1(neutron), 1D(deuterium) etc.
  • Emissions: Particles ejected in artificial transmutation along with recoil nucleus is called as emissions.
  • Recoil atom or recoil nucleus: Atom produced in an artificial transmutation having a nearly same atomic number and mass number as that of the target atom is called as recoil nucleus.
  • More examples with different projectiles are given below.

Using  α – particles as projectile:

Nuclear Reactions 02

 

Using Protons as Projectile:

 



Nuclear Reactions 03

Using Deuterons as Projectile:

 

Nuclear Reactions 04

Using Neutrons as Projectile:

Nuclear Reactions 05



Neutrons are the Best Projectiles:

  • The process of conversion of the nucleus of an atom one element into that of another element by using high-velocity projec­tiles is called as artificial transmutation. There is a positive charge on the nucleus while the negative charge is carried by extranuclear electrons.
  • There is a positive charge on the particles like protons and deuterons. Due to the positive charge on them, they experience a greater force of repulsion while penetrating the positively charged nucleus of the target atom.
  • Neutrons do not carry any charge. Due to chargeless nature, they are not deflected by extranuclear electrons similarly they are not repelled by the positive charge of the target nucleus. Hence neutrons are easily absorbed by the nucleus and the transmutation is carried out effectively. Hence neutrons are the best projectile in the transmutation of elements.

Artificial or Induced Radioactivity:

  • The process of conversion of a stable non-radioactive atom of one element into an unstable radioactive atom of another element by bombardment with high-speed projec­tile is called induced or artificial radioactivity.
  • The recoil atom decays at its own rate. The radioactivity exhibited by recoil nucleus itself is called artificial radioactivity.
  • In certain artificial transmutation reactions, product undergoes spontaneous disintegration even on stoppage of bombardment of projectile.  During such nuclear reactions positrons ( +1 e0),  neutrons  (0n1), electrons (-1 e0) or  γ rays are emitted.
  • Some of the induced radioactivity reactions using different projectiles are,

Using  α – particle (2He4):

Nuclear Reactions 06

 

Using protons (1H1):

 

Nuclear Reactions 07



Using Deuterons (1D2):

Nuclear Reactions 08

Using neutrons :

Nuclear Reactions 09

 

Natural Radioactivity:

  • The phenomenon of spontaneous and continuous and uncontrollable disintegration of an unstable nucleus accompanied by the emission of active radiations is called natural radioactivity.
  • It is spontaneous process shown by nuclei of heavy elements with atomic number greater than 83.
  • α, β, γ rays are emitted.
  • No naturally occurring radioisotope emits positrons.
  • I daughter element is radioactive hence it further undergoes disintegration and a series of radioelements is obtained.
  • This reaction cannot be controlled as it is independent of external factors.
  • Very large amount of energy is released.

Artificial Radioactivity:

  • The process of conversion of a stable non-radioactive atom of one element into an unstable radioactive atom of another element by bombardment with high-speed projec­tile is called induced or artificial radioactivity.
  • It is a non-spontaneous process.
  • Positrons ( +1 e0),  neutrons  (0n1), electrons (-1 e0) or  γ rays are emitted.
  • No artificially synthesised radioisotope emits α particles.
  • Daughter element is non-radioactive hence a series of radioelements is not obtained.
  • By controlling the flow of projectiles the number of nuclei undergoing artificial transmutation can be controlled.
  • A small amount of energy is released.
  • Artificial radioactivity can be introduced into lighter nuclei.

 



Nuclear Fission:

  • Nuclear fission is a process in which heavy nuclei break into lighter fragments of elements giving a very large amount of energy.

Nuclear Reactions 10

  • This reaction is used in atom bomb in an uncontrolled manner while it is used in a nuclear reactor in controlled manner.

Nuclear Fusion:

  • Nuclear fusion is a process in which nuclei of lighter elements combine to form a nucleus of the heavier element.

Nuclear Reactions 11

  • This process is used in the production of a hydrogen bomb.

 

One Comment

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