Introduction of Artificial Transmutation
The process of converting one element into another by bombarding it with fundamental particles is called artificial transmutation. The very first artificial element produced by the process of artificial transmutation was oxygen. Thus, in simple words, it is the process of transformation of one particular element into another by the making use of artificial means. For getting an element of oxygen, the nucleus of nitrogen was bombarded with an alpha particle. Normally, the element that is produced through the process usually exhibits radioactivity which results in induced radioactivity. The particles that you can use for bombardment are:
α-particle; Proton and Deuteron: 1H3, Neutron 0n1
Process of Artificial Transmutation
Now, as we read above, the new or artificial element that is produced by the process of artificial transmutation exhibits radioactivity, which results in induced radioactivity. Usually, the particles that are bombarded with the main element are, α-particle; Proton, and Deuteron, Neutron, Alpha particles, deuterons and protons, they all carry nuclei that are positively charged. They are not suitable projectiles because they all repel positively charged nuclei.
Neutrons, on the other hand, possess no charge at all, and hence considered the best projectile for the artificial transmutation process. When the main element or the targeted element is bombarded with a neutron, the resulting element or product shall depend upon the speed of the neutron with which it is bombarded. The bombardment is slow; the neutrons penetrate into the nucleus of the targeted element. When the bombardment speed is high the neutrons pass through the nucleus. The other name of a slow neutron is the thermal neutron. In producing a nuclear reaction, the slow neutrons are more effective than the high-speed neutrons.
Who Discovered Artificial Transmutation?
On June 2nd, under the guidance of the Junior Scientific Club, the annual Boyle lecture was delivered by Lord Rutherford who took the “Artificial Transmutation of the Elements” as his subject . He described the pioneer achievements of Messrs, Cockcroft, and Walton at the Cavendish Laboratory in applying the high voltage method of generating fast streams of protons for producing atomic transformation and detailed recent developments of method by which it was possible to obtain still greater results at a lower voltage. Further modifications have led to conclusions of high interest, and the new type of projectile results in extending the knowledge factor of types of possible transformation, most of which is now in use.
It was probable that further assaults would be made on the stability of the nucleus shown, and there was particular evidence of the appearance of a more positively charged particle of mass comparable with that of the negative electron. The bombarding projectiles are imparted with high energy before bombarding the target nucleus by the device called Particle accelerator, like linear accelerator, cyclotron, synchrotron, etc.
Ernest Rutherford was one of the pioneers who discovered artificial transmutation. He discovered the following by exposing the nitrogen atoms to alpha particles. He bombarded the said nitrogen nucleus with the present alpha particles in order to get oxygen.
Rutherford allowed α -particles to pass through different glasses. He studied the different processes that may happen. The apparatus consists of a thick glass chamber A provided with an adjustable rod, carrying a radioactive substance R. The side of the glass tube facing R is covered by a metal plate with a central hole which is closed by a thin silver foil. A screen S coated with a fluorescent material like zinc sulfide is arranged in front of the silver foil and the scintillations produced on it can be observed through the microscope M. The radioactive substances emit α -particles whose range in the air is roundabout 8cm. When the glass tube is filled with nitrogen gas, scintillations are observed even when R is at a distance of 40cm from the foil. These particles produce scintillations and it cannot be α -particles because they cannot have such a long range. A further analysis proved that each of these particles had a mass which was nearly equal to that of a hydrogen atom and carried a positive charge equal to that of an electron. The new particles were named as protons.
When a nitrogen nucleus is hit by an α (42He ) -particle, it disintegrates into an oxygen nucleus with a proton 11H . The nuclear reaction can be represented as
\[N_{7}^{14} + He_{2}^{4} \rightarrow O_{8}^{17} + H_{1}^{1}\]
The light elements from boron to potassium, with the exception of carbon and oxygen, will be transmuted by bombarding with α -particles ( 42He ).
In fact, the first nuclear transmutation was also witnessed and applied to the branch of modern physics by Frederick Soddy. He was working with Rutherford in the year 1901, and they both discovered that radioactive thorium could transform itself into radium. They were excited to witness that the process was transmutation and Soddy worked on it further to apply it to the branch of Physics.
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Some Prominent Examples of Artificial Transmutation
When an alpha particle is bombarded with the nucleus of a nitrogen element, oxygen as an artificial element is produced. As a part of transformation, one atom of hydrogen is also produced.
When an alpha particle is bombarded with the nucleus of an aluminum element, phosphorus as an artificial element is produced. As a part of the transformation, a neutron is produced.
When Uranium-28 is bombarded with neutrons, the resultant element is Uranium-239. Uranium-239 is very unstable; therefore, it decays to Neptunium. When it decays, it produces beta particles.
Conversion Laws Applied to Nuclear Reactions
While studying artificial transmutation, it is necessary to keep a note on “conversion laws” that are applied to a nuclear reaction.
The number of nucleons in a nuclear reaction stays the same or is conserved.
The mass–energy relation is conserved.
The charge is conserved, to understand it differently, the sum of charges on the left-hand side of the reaction is equal to the number of charges on the right-hand side.
Artificial Transmutation Equation
The artificial transmutation equation is based upon the conversion laws as noted above. It represents the conversion of one element into the other. The reaction is shown with the number of protons. The element which is to be converted by bombardment is kept at the left-hand side along with the fundamental particle that has to be bombarded, on the right-hand side comes the final element along with the subatomic particles. An example of this can be:
When you bombard Uranium-238 with a neutron, it will convert into Uranium -239, it is highly unstable and transmutes into Neptunium which can be seen emitting a beta participle.
Difference Between Artificial Transmutation and Artificial Radioactivity
In artificial transmutation, one element, which is a non-radioactive element, is converted into a final element by bombarding a fundamental particle through artificial means. While in artificial radioactivity, the radioactivity is induced in a stable element, and the whole process undergoes numerous nuclear reactions.
FAQs on Artificial Transmutation
1. What is the definition of artificial transmutation in Physics?
Artificial transmutation is the process of converting the nucleus of one element into the nucleus of another element through artificial means. This is achieved by bombarding a stable target nucleus with high-energy particles, such as alpha particles, protons, or neutrons, using devices like particle accelerators. This process is distinct from natural radioactive decay as it is an externally induced transformation.
2. What is a classic example of an artificial transmutation reaction?
A classic example is the first-ever artificial transmutation conducted by Ernest Rutherford in 1919. He bombarded a stable Nitrogen-14 nucleus with a high-energy alpha particle (Helium nucleus). This resulted in the creation of an Oxygen-17 isotope and the emission of a proton (Hydrogen nucleus). The balanced nuclear equation for this reaction is: 147N + 42He → 178O + 11H.
3. How does artificial transmutation differ from natural radioactive decay?
The primary difference lies in their initiation. Artificial transmutation is a forced, man-made process that requires an external high-energy particle to bombard and change a stable nucleus. In contrast, natural radioactive decay is a spontaneous process where an inherently unstable nucleus decays on its own to reach a more stable state, without any external intervention.
4. Why are neutrons considered the most effective projectiles for inducing artificial transmutation?
Neutrons are considered highly effective projectiles because they are electrically neutral. Unlike positively charged protons or alpha particles, neutrons are not repelled by the positive charge of the target nucleus. This lack of electrostatic repulsion allows them to penetrate the nucleus more easily, even at lower kinetic energies (as thermal neutrons), significantly increasing the probability of inducing a transmutation.
5. What are the fundamental requirements for carrying out artificial transmutation?
To perform artificial transmutation, three key components are essential:
- A stable target nucleus that is to be transformed.
- A projectile particle, such as a proton, neutron, or alpha particle, to bombard the target.
- A particle accelerator (like a cyclotron or linear accelerator) to provide the projectile with enough kinetic energy to overcome any repulsive forces and interact with the target nucleus.
6. What are the key conservation laws that must be obeyed in any artificial transmutation equation?
Every artificial transmutation must adhere to fundamental conservation laws, ensuring the nuclear equation is balanced:
- Conservation of Charge: The sum of the atomic numbers (protons) of the reactants must equal the sum of the atomic numbers of the products.
- Conservation of Mass Number: The sum of the mass numbers (total nucleons) of the reactants must equal the sum of the mass numbers of the products.
- Conservation of Mass-Energy: The total energy, including rest mass energy (E=mc²), is conserved throughout the reaction.
7. What is the relationship between artificial transmutation and induced radioactivity?
Artificial transmutation is often the cause of induced radioactivity. When a stable nucleus is transmuted, the resulting product nucleus is frequently an unstable isotope. This new, unstable nucleus then seeks stability by undergoing radioactive decay (e.g., beta or gamma decay). This radioactivity, which has been 'induced' in a previously stable element, is known as induced or artificial radioactivity. Thus, transmutation is the initial step that can create a new radioactive element.
8. How is artificial transmutation used to create transuranic elements?
Transuranic elements are elements with an atomic number greater than 92 (Uranium) and are not typically found in nature. They are synthesized using artificial transmutation. This is done by bombarding heavy nuclei, like Uranium-238 or Plutonium-239, with particles, most commonly neutrons, inside a nuclear reactor or particle accelerator. The target nucleus captures the projectile, transmuting into a heavier, unstable element which may then decay into the desired transuranic element. For example, bombarding U-238 with a neutron produces U-239, which then beta-decays to Neptunium (Np, Z=93).
