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Physics

Nuclear reactions – Nuclear Fission and Nuclear Fussion

Nuclear Reactions

Rutherford in 1919 transmitted nitrogen isotope into an oxygen isotope. The nitrogen was subjected to the action of swift alpha – particles derived from radium salt.

Transmutation is the process by which radioactive elements change into different elements.

Nuclear reaction is a process in which two nuclei or nuclear particles collide, to produce different products than the initial particles.

Nuclear fission and nuclear fusion both are nuclear phenomena that release large amounts of energy, but they are different processes which yield different products. Learn what nuclear fission and nuclear fusion are and how you can tell them apart.

Nuclear Fission

Nuclear fission takes place when an atom’s nucleus splits into two or more smaller nuclei. These smaller nuclei are called fission products. Particles (e.g., neutrons, photons, alpha particles) usually are released, too. This is an exothermic process releasing kinetic energy of the fission products and energy in the form of gamma radiation. Fission may be considered a form of element transmutation since changing the number of protons of an element essentially changes the element from one into another.

Nuclear Fission Example:

23592U + 10n → 9038Sr + 14354Xe + 310n

Nuclear Fusion

Nuclear fusion is a process in which atomic nuclei are fused together to form heavier nuclei. Extremely high temperatures (on the order of 1.5 x 107°C) can force nuclei together. Large amounts of energy are released when fusion occurs.

Nuclear Fusion Examples

The reactions which take place in the sun provide an example of nuclear fusion:

11H + 21H → 32He

32He + 32He → 42He + 211H

11H + 11H → 21H + 0+1β

Comparison between Nuclear Fission and Fusion

Nuclear FissionNuclear Fusion
Definition:Fission is the splitting of a large atom into two or more smaller ones.Fusion is the fusing of two or more lighter atoms into a larger one.
Natural occurrence of the process:Fission reaction does not normally occur in nature.Fusion occurs in stars, such as the sun.
Byproducts of the reaction:Fission produces many highly radioactive particles.Few radioactive particles are produced by fusion reaction, but if a fission “trigger” is used, radioactive particles will result from that.
Conditions:of the substance and high-speed neutrons are required.High density, high temperature environment is required.
Energy Requirement:Takes little energy to split two atoms in a fission reaction.Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.
Energy Released:The energy released by fission is a million times greater than that released in chemical reactions; but lower than the energy released by nuclear fusion.The energy released by fusion is three to four times greater than the energy released by fission.
Nuclear weapon:One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb.One class of nuclear weapon is the hydrogen bomb, which uses a fission reaction to “trigger” a fusion reaction.

Comparison of Nuclear Reaction and Ordinary Chemical Reaction

Nuclear ReactionOrdinary Chemical Reaction 
During nuclear reactions, the nuclei of atoms undergo change and therefore new elements are formed as a result of such reactions.During chemical reactions, elements do not lose their identity. In these reactions, only the electrons in the outermost shell of atoms participate whereas the nuclei of atoms remain unchanged.
Reactivity of an element towards nuclear reactions is nearly independent of oxidation state of the element. For example, Ra element or Ra2+ ion in RaC2 behave s similarly during nuclear reactions.Reactivity of an element towards chemical reactions depends upon the oxidation state of the element. In ordinary chemical reactions, Ra and Ra2+ behave quite differently.
In nuclear reactions, isotopes behave quite differently. For example, U-235 undergoes fission quietly readily but U-238 does not.Different isotopes of an element have nearly same chemical reactivity. 
Rate of a nuclear reaction is independent of temperature and pressure.Rate of a chemical reaction is largely affected by temperature and pressure.
A nuclear reaction cannot be reversedA chemical reaction can be reversed.
Nuclear reactions are accompanied by large energy changes.Chemical reactions are accompanied by relatively small energy changes.

Assessment

What is the most significant difference between Nuclear fission and fusion?

What does Transmutation mean?

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