What is Nuclear Chemistry?
The field of chemistry dealing with radioactivity, nuclear processes and transformation is known as nuclear chemistry. These processes take place in the nuclei of the atom.
The study of physical and chemical characteristics of an element due to change in the structure of the atomic nucleus due to some nuclear reaction and the release of energy and its uses, all comes under nuclear chemistry. It is also known as radiochemistry.
Atoms are composed of three fundamental particles, which are, protons, electrons and neutrons. These are the sub-atomic particles. For the physical, chemical and nuclear behaviour of atoms these sub-atomic particles are responsible. By the interaction of two nuclei, a nuclear reaction occurs. It occurs due to the impact of sub-atomic particles on the nucleus.
In a nuclear reaction, one atom is converted into another atom. During the nuclear reaction, a huge amount of energy is released. The sub-atomic particle with a positive charge is called a proton, the one with a negative charge is the electron and the sub-atomic particle having no net electrostatic charge is the neutron. Except for hydrogen, the neutron is present in the nucleus of all the atoms.
Nuclear fission and nuclear fusion
- Nuclear fission: In such a type of reaction, an atom's nucleus split occurs and it converts into smaller particles; huge amount of energy is released.
- Nuclear fusion: In such a type of reaction, a fusion of two or more elements into a larger element occurs; a large amount of energy is released.
Nuclear chain reactions
The process in which the release of a neutron occurs in a series of many fission processes as a result of which a huge amount of energy is released is called nuclear chain reactions. These reactions majorly occur with heavy radioactive elements.
- It is the process of spontaneous and uncontrollable annihilation involving the process of emission of active radiations from an unstable atomic nucleus.
- When the radiations are given out during nuclear reactions, the process is known as alpha decay, beta decay or the gamma decay depending on the type of radiations coming out.
- S.I. unit of radioactivity is Becquerel and 1 Bacquerel is the nuclar disintegration occurring in one second.
Radioactive decay is defined as the number of radioactive atoms disintegrating per unit of time. It is directly proportional to the number of radioactive atoms present at a given instant. Expression for the decay constant is:
- N0 is the number of radioactive atom present initially
- Nt is the number of radioactive atoms present after time t.
- y is the decay constant.
The time needed for the disintegration of half of the original amount of radioactive substance is defined as a half-life period.
Average life or mean life
Within experimental limits, the time till which radioactive decay can be recorded is known as average life or mean life. The reciprocal of the decay constant is the average life.
Nuclear stability depends on the following factors such as nuclear forces, mass defect and binding energy, stability and instability of nuclei, neutron and proton ratio.
In nuclear power plants, the property of nuclear reaction, that is to emit high energy radiations, is used to obtain energy. The following radiations occur in general:
Alpha rays bent towards negative plates having a positive charge. In alpha radiations, an alpha particle is emitted from an atom's nucleus. Two protons and two neutrons are present in alpha particles. It possesses similarity to the helium nucleus. The atomic mass of an atom decreases by 4 when the alpha particle is emitted from the atom.
Properties of alpha radiations
- Alpha particles consist of positively charged rays.
- +2 charge and mass of 4 units is there in alpha particle.
- About 1/10 velocity of light is of alpha rays.
- Due to their high kinetic energy, they have high ionizing power.
- The least penetrating power is present in alpha rays.
- Deflection occurs in an electric and magnetic field.
- The affect occurring on a photographic plate is less.
Beta rays bent towards positive plates having a negative charge. It involves the transfer of neutron. The mass of the atom will not change when the beta particle is emitted. The atomic number increases by 1.
Properties of beta radiations
- Beta particle consists of negatively charged particles.
- -1 charge is present in beta particles and has negligible mass.
- It has a velocity of 9/10 of light.
- Low ionizing power is present due to low kinetic energy.
- Due to their small size and higher velocity, high penetration power is present.
- High deflection is seen in an electric and magnetic field.
- Due to low kinetic energy, lower luminosity in ZnS is produced.
- The affect occurring on a photographic plate is more.
Gamma rays pass straight does not bend towards the negative or positive charge. In this, electromagnetic energy is emitted from the atoms nucleus. No particles are emitted and thus it does not result in the transmutation of atoms.
Properties of gamma radiations
- Gamma rays comprise electromagnetic radiation.
- The charge is not present in gamma rays.
- Its velocity is higher than light.
- Due to their low kinetic energy, less ionizing power is present.
- Due to it higher velocity penetration power is high.
- In electric and magnetic it remains unelected.
- Due to its low kinetic energy, it produces less luminosity in ZnS.
Context and Applications
This topic is significant in the professional exams for both undergraduate and graduate courses, especially for Bachelors and Masters in Chemistry.
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