Nuclear Chemistry - Types, Nuclear Fission and Fusion and Applications
The discovery of radioactivity opened up the way for the creation and development of nuclear chemistry in the early twentieth century. In the mid-twentieth century, novel findings and the Second World War ushered in the Nuclear Age. From nuclear power generation to war damage, nuclear chemistry has shown tremendous potential. The wide proliferation of the area has brought about a wide variety of nuclear chemistry topics - what is nuclear chemistry, nuclear radiations, artificially simulated nuclear reactions (fission and fusion), and the uses of nuclear chemistry.
Nuclear Chemistry
Nuclear chemistry is the study of the chemical and physical properties of elements that deal with nuclear reactions or reactions that happen inside the structure of the nucleus. Modern nuclear chemistry sometimes referred to as radiochemistry, has become highly interdisciplinary in its applications, from the study of element formation in space to the design of radiopharmaceuticals for diagnostic medicine. In fact, the chemical technology developed by nuclear chemists has become so important that biologists, geologists, and physicists use nuclear chemistry as a common tool in their disciplines.
Nuclear chemists can be found in a variety of research areas, including nuclear imaging and nuclear technology. They often work to improve the efficiency and safety of nuclear energy sources and the way radioactive materials are stored and disposed of.
Nuclear chemists carry out basic research, applied research, or theoretical research. You often work in the laboratory and may be responsible for the operation, maintenance, and repair of state-of-the-art equipment. You are also responsible for the maintenance of sample preparation materials and equipment, and for the safe use and disposal of samples and other materials used in the laboratory.
Marie Curie, who was the founder of nuclear chemistry, was intrigued by Antoine Henri Bekrel's discovery that photographic film can emit light that can be exposed even when uranium minerals are wrapped in black paper. Using an electrometer that could measure the electrical conductivity of air (the predecessor of the Geiger counter) invented by her husband Pierre and his younger brother Jack, she was able to prove that thorium also produces these rays. This process is what she called radioactivity.
What Is Nuclear Chemistry?
Nuclear chemistry is a sub-discipline of chemistry dealing with the study of changes in the nucleus of atoms of elements. These nuclear changes are a source of nuclear power and radioactivity, and the energy released from the nuclear reactions has far-reaching applications. Nuclear chemistry is also termed radiochemistry, which involves the study of the elements composing the universe, design, and development of radioactive drugs for medicinal uses, and several other scientific applications.
Nuclear Radiations
Nuclear radiation refers to the photons and particles that are emitted during nuclear reactions. The particles emitted in nuclear reactions possess an energy that is tremendous enough to knock electrons from atoms and molecules, thereby ionizing them. For this reason, nuclear radiation is also known as ionizing radiation.
Nuclear radiations include alpha rays, beta rays, and gamma rays. Nuclear reactions release ionizing subatomic particles, including alpha particles, neutrons, beta particles, mesons, muons, positrons, and cosmic rays. For example: during Uranium-235 fission, the nuclear radiation that is emitted contains gamma-ray photons and neutrons.
Types of Radiations
Alpha Radiation: Alpha radiation is the emission of alpha particles when an atom goes through radioactive decay. An alpha particle consists of two protons and two neutrons and is similar to a Helium-4 atom. Thus, the resulting element has an atomic number less by two units and an atomic mass less by four units than that of the originating element. Example: Uranium-238 undergoes alpha decay in the following manner:
23892U → 23490Th + 42He
Beta Radiation: Consists of a stream of high-speed electrons. Beta-decay is of two types –beta plus and beta minus. In beta plus decay, the nucleus emits a positively charged electron (positron) and a proton that is converted into a neutron (neutrino). In beta minus decay, the nucleus emits a neutron that is transformed into a proton (antineutrino) and an electron.
Beta minus decay: 1n → 1p+ + 0-1β- + v̅
Beta plus decay: 11p+ → 10n + 01β + v
127N ⟶ 612C + 01β+
146C ⟶ 147N + 0-1β
Gamma Radiation: Gamma radiation (γ) does not consist of any particles. Instead, it involves photons of energy being emitted from an unstable radioactive nucleus. Gamma rays are electromagnetic radiations of short wavelengths and have no charge or mass. These rays represent the loss in energy when the remaining nucleons undergo stable rearrangements, and thus, gamma rays accompany other radioactive emissions. Example:
23892U → 23490Th + 42He + 200γ
Nuclear Fission
Nuclear Fission is an artificially simulated nuclear reaction where a heavy nucleus splits into two lighter nuclei. Fission was discovered by bombarding a sample of Uranium-235 with neutrons, which resulted in the production of lighter elements like Barium. In a typical nuclear chain reaction, each dividing nucleus releases more than one neutron, which, in turn, collides with neighboring nuclei and induces a succession of self-sustaining nuclear fission reactions. The fission rate increases geometrically with each generation of events.
(image will be uploaded soon)
Nuclear Fusion
Nuclear Fusion is also an artificially simulated nuclear reaction in which two or more nuclei of elements combine to produce a heavier and more stable nucleus. The initiation of the fusion process requires very high temperatures, which are obtained from nuclear fission reactions. Nuclear Fusion generates explosive amounts of energy, which is the source of power for the sun and all the stars. Examples: deuterium-deuterium (D-D) fusion, deuterium-tritium (D-T) fusion.
2 21H → 32He + 10n
21H + 31H → 42He + 10n
Nuclear Radiations
Nuclear radiation is the phenomenon of particles being emitted by atomic nuclei in the form of alpha rays, beta rays, gamma rays.
The particles emitted during a nuclear reaction are strong enough to ionize the electrons by removing them from atoms and molecules.
Types of Radiations
Alpha Radiations
Alpha rays are heavy particles and have a very short range, so they don't go that far. This means that alpha particles cannot penetrate even a piece of paper. Alpha particles outside the body do not even pass through the surface of the skin. However, inhaling or ingesting substances that emit alpha particles can expose delicate tissues such as the lungs. For this reason, high-level radon in your home is considered a problem.
Beta Radiations
Beta particles can travel a little further than alpha particles. You can use a relatively small shield to stop them. They can get into your body, but they can't penetrate it completely through it. To be useful in medical imaging, beta particles must be released through substances injected into the body. If radioactive substances can be introduced into tumors, they will also be very useful in treating cancer.
Gamma Radiations and X-rays
Gamma rays and X-rays are highly penetrating electromagnetic radiation that can penetrate through the body. They are proven to be useful in a medicine-to show if the bones are broken, where the cavities are, or to identify the tumor. Shields made of high-density materials such as concrete and lead are used to avoid exposure to sensitive internal organs and those who may handle this type of radiation.
Applications of Nuclear Chemistry
Agriculture
Plant mutation breeding to achieve improved nutrition and food security.
Management of fertilizer use through Radiolabelling.
Controlling insect populations.
Consumer products
Smoke detectors, non-stick materials, clocks, and watches utilize radioisotopes.
Food
Food irradiation with gamma rays to prevent spoilage and enhance shelf-life.
Pest control.
Industry
Radioactive tracers find use in industrial processes.
Inspection of instruments.
Carbon dating.
Nuclear desalination of water.
Medicine
MRI scans, CT scans, and X-rays for diagnosis.
Radioactive Iodine is used for the treatment of cancers.
Sterilization of medical instruments.
Transport
Nuclear-powered submarines and ships.
Radioisotope thermal generators for electricity production in space missions.
FAQs on Nuclear Chemistry
1. What is nuclear chemistry?
Nuclear chemistry is a branch of chemistry that studies the changes occurring within the nucleus of an atom. It focuses on nuclear reactions, radioactivity, and the properties of nuclear particles. Unlike traditional chemistry which deals with electron interactions, nuclear chemistry involves transformations of the elements themselves, releasing substantial amounts of energy.
2. What is the difference between nuclear fission and nuclear fusion?
Nuclear fission and fusion are two types of nuclear reactions that release enormous energy, but they operate on opposite principles. Nuclear fission is the process where the nucleus of a heavy, unstable atom (like Uranium-235) splits into two or more lighter nuclei. In contrast, nuclear fusion is the process where two light atomic nuclei combine to form a single, heavier nucleus, a reaction that powers the sun and other stars.
3. What are the main types of nuclear radiation?
The three primary types of nuclear radiation, each with distinct properties, are:
- Alpha (α) radiation: Consists of heavy, positively charged particles (two protons and two neutrons) with low penetrating power, easily stopped by a sheet of paper.
- Beta (β) radiation: Consists of high-speed electrons or positrons that are more penetrating than alpha particles but can be stopped by thin metal or plastic.
- Gamma (γ) radiation: High-energy electromagnetic waves (photons) with no mass or charge. They are highly penetrating and require dense materials like lead or concrete for effective shielding.
4. What are some key applications of nuclear chemistry in various fields?
Nuclear chemistry has numerous practical applications, including:
- Medicine: Used in diagnostic imaging like MRI and CT scans, and for cancer treatment through radiotherapy.
- Energy: Nuclear fission is used in power plants to generate electricity.
- Industry: Techniques like carbon dating help determine the age of ancient artifacts, and radioactive tracers are used to monitor industrial processes.
- Agriculture: Used to sterilise pests, irradiate food to extend shelf life, and study fertilizer efficiency.
- Consumer Products: Found in items like smoke detectors, which use a small amount of a radioisotope to detect smoke particles.
5. What is transmutation in the context of nuclear chemistry?
Transmutation is the conversion of an atom of one element into an atom of another element. This occurs through nuclear reactions, either spontaneously via radioactive decay or artificially by bombarding a nucleus with high-energy particles. For example, bombarding nitrogen-14 with an alpha particle can transmute it into an oxygen-17 atom and a proton.
6. How do nuclear reactions fundamentally differ from ordinary chemical reactions?
Nuclear and chemical reactions differ in several key ways:
- Particles Involved: Chemical reactions involve the rearrangement of valence electrons, while nuclear reactions involve changes within the atomic nucleus (protons and neutrons).
- Element Identity: In chemical reactions, atoms are rearranged but the elements remain the same. In nuclear reactions, atoms of one element are often converted into atoms of another.
- Energy Changes: Nuclear reactions release amounts of energy that are millions of times greater than the energy released in chemical reactions.
- Influencing Factors: Chemical reaction rates are affected by temperature, pressure, and catalysts. Nuclear reaction rates are generally unaffected by these external conditions.
7. Why is a chain reaction essential for a self-sustaining nuclear fission process?
A chain reaction is essential because it allows the fission process to sustain itself without continuous external intervention. When a heavy nucleus like uranium fissions, it releases energy and two or more neutrons. These newly released neutrons can then trigger the fission of other nearby uranium nuclei. This creates a cascading effect where each fission event initiates further fissions, leading to a continuous, self-propagating release of energy, which is the core principle behind nuclear power reactors.
8. How do the different types of nuclear radiation (alpha, beta, gamma) vary in their biological hazard level?
The biological hazard depends on both the type of radiation and the nature of exposure. Externally, gamma rays are the most dangerous due to their high penetrating power, as they can easily pass through skin and damage internal organs. Internally, if a substance is inhaled or ingested, alpha particles are extremely hazardous. Although they cannot penetrate skin, their heavy mass and charge cause intense, localized damage to sensitive tissues like the lungs over a very short range.
9. Why is achieving controlled nuclear fusion on Earth so much more difficult than achieving controlled nuclear fission?
Achieving controlled nuclear fusion is exceptionally difficult because it requires overcoming the immense electrostatic repulsion between positively charged atomic nuclei. To force them to fuse, you must replicate the conditions inside a star, which means creating and containing matter at extremely high temperatures (over 100 million °C) and pressures. Fission, by contrast, is initiated by a neutral particle (a neutron) striking an already unstable heavy nucleus, a process that does not require overcoming such a massive repulsive force and is therefore far easier to control.
10. Who is considered a key pioneer in nuclear chemistry and what was their foundational discovery?
Marie Curie is considered a foundational pioneer of nuclear chemistry. Her most significant contribution was the discovery and characterization of radioactivity. She was the first to coin the term and proved that rays were emitted from the atoms themselves, not from an interaction between molecules. This revolutionary idea that atoms were not immutable laid the groundwork for the entire field of nuclear science.
