Radioactivity is the spontaneous emission of highly penetrating radiations from heavy elements occurring in nature. The radiations emitted by radioactive substances are studied by conducting experiments in which a small hole is drilled in a lead block and a narrow beam of radiation emerges out of the hole. The nature of the radiation is studied by applying an electric or magnetic field, which causes the narrow beam to split into three components: α-particles, β-particles, and γ-rays.
Alpha decay, beta decay, gamma decay, positron emission, and electron capture are all considered as types of radioactive decay. Alpha particles are positively charged and are nuclei of helium atoms. They have a rest mass of 6.4 × 10-27 kg and ionize the gas through which they pass. Beta particles are negatively charged and are electrons of nuclear origin. They have a rest mass of 9.1 × 10-31 kg and have a penetrating power 100 times more than that of alpha particles. Gamma particles are chargeless and are electromagnetic waves of very short wavelength. They have a penetrating power higher than that of alpha and beta particles.
The cause of radioactivity is the unstable nucleus of the radioactive element, which emits radioactive radiations due to the repulsive force being greater than the attractive force. The properties of radioactive radiations depend on the type of radiation emitted and include the ability to ionize gases, produce fluorescence and phosphorescence on certain materials, affect photographic plates, and induce artificial radioactivity.
Artificial Radioactivity
Apart from natural radioactivity, there is another type of radioactivity that is induced artificially, known as artificial radioactivity. It occurs when atomic nuclei are bombarded with subatomic particles, such as protons, neutrons, or alpha particles, causing nuclear reactions that result in the formation of radioactive isotopes.
For example, when boron is bombarded with alpha particles, it undergoes nuclear transmutation and becomes a radioactive isotope of nitrogen:
14N + α → 17O + proton
The resulting isotope of oxygen, 17O, is radioactive and will decay into a stable isotope of nitrogen, 17N, by emitting beta particles:
17O → 17N + β-
Radioactive Decay
Radioactive decay is the process by which a nucleus undergoes a change in its composition by emitting radiation. There are five types of radioactive decay, as mentioned in the note:
1. Alpha decay: In alpha decay, a nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons.
2. Beta decay: In beta decay, a nucleus emits a beta particle, which is either an electron or a positron.
3. Gamma decay: In gamma decay, a nucleus emits a gamma ray, which is a high-energy photon.
4. Positron emission: In positron emission, a nucleus emits a positron, which is a particle with the same mass as an electron but with a positive charge.
5. Electron capture: In electron capture, a nucleus captures an electron from its inner shell, combining with a proton to form a neutron.
Properties of Radioactive Radiation
Each type of radioactive radiation has its own unique properties, as summarized in the note. Alpha particles are positively charged and have a high ionizing power but low penetrating power. Beta particles are negatively charged and have a higher penetrating power than alpha particles but lower ionizing power. Gamma rays are neutral and have a very high penetrating power but lower ionizing power than alpha and beta particles.
Cause of Radioactivity
Radioactivity occurs when the forces within the nucleus of an atom are unbalanced, leading to an unstable nucleus. If the repulsive force between protons is too strong, the nucleus will decay by emitting radiation until it becomes more stable. This is why heavy elements, which have a large number of protons and are thus more likely to have unstable nuclei, are more likely to be radioactive.
The radiation emitted by radioactive elements can have harmful effects on living organisms and the environment. This is because the ionizing radiation can ionize atoms and molecules in the cells of living organisms, causing damage to the DNA and other cellular structures. This can result in mutations, cancer, and other health problems.
Therefore, it is important to handle radioactive materials with care and to minimize exposure to them. This is done by using shielding materials such as lead and concrete, wearing protective clothing and using specialized equipment when working with radioactive materials, and following proper safety protocols.
In addition to natural radioactivity, artificial radioactive materials can also be produced through nuclear transmutation, which involves changing the nucleus of an atom through processes such as nuclear fission or fusion. These processes are used in nuclear power plants and nuclear weapons, and the resulting radioactive materials must be handled and disposed of carefully to prevent harm to humans and the environment.
Overall, the study of radioactive radiations is important for understanding the behavior and properties of radioactive materials, as well as for developing methods for their safe handling and disposal.
Chapter: Radioactivity and Nuclear Radiation
