Understanding Isotopes, Radioactivity, and Nuclear Reactions
Isotopes, Radioactivity, and Nuclear Reactions
Isotopes: Are atoms with the same atomic number but different atomic mass.
Radioactivity: The ability of some unstable nuclei to emit particles and/or electromagnetic radiation spontaneously. All nuclei with an atomic number greater than 83 are radioactive.
Internal Radiation: Internal radiation comes from radioactive substances in food, water, and air, which, when ingested or inhaled, are absorbed in living tissue. The main radioactive isotopes contained in the human body are potassium-40, carbon-14, and tritium.
Radon: Continuously emanating from the Earth’s surface. Radon is a gas and is therefore inhaled. When this element is trapped in a compound, its concentration may increase significantly and cause damage to living beings.
Types of Radioactive Emissions
Alpha Particles: Alpha particle emissions have low speed and low penetration power because of their high mass, resulting in low velocity. They consist of two protons and two neutrons. Alpha particles are highly ionizing because they can strip electrons from atoms, causing ionization.
Beta Particles: They are much smaller than alpha particles and more penetrating, due to their greater speed, approaching that of light (traveling at one-tenth of the speed of light). Beta decay occurs in nuclei with an excess of neutrons or protons; the nucleus stabilizes by adjusting the number of protons or neutrons. Beta particles have mass and charge identical to electrons.
Gamma Radiation: Electromagnetic radiation is also pervasive and has no electrical charge. Gamma rays are highly mutagenic to living cells. They travel at the speed of light and are of high frequency. Gamma radiation is manifested in radioactive processes as a result of the de-excitation of a nucleus that has previously been excited. Therefore, processes that produce alpha or beta particles are accompanied by the emission of electromagnetic radiation in the form of photons (gamma particles).
Nuclear Reactions
Nuclear reactions are caused by an unstable nucleus, called the parent nucleus, which emits radiation and spontaneously transforms into a more stable nucleus, called the daughter nucleus. Radioactive decay is represented by the general equation:
- High-mass nuclei (Z > 83): Release alpha particles (α).
- Nuclei with an excess of neutrons compared to protons: Release beta particles (β).
- Nuclei with an excess of protons: Transform into neutrons, releasing positrons (+1 e0) or positive beta particles.
Half-Life (t1/2): Defined as the speed at which nuclear decay occurs, it is the time required for the concentration of a reactant to decrease to half its initial concentration.
Nuclear Fission and Fusion
Nuclear Fission: This occurs when a heavy nucleus (Z > 200) divides to form smaller, more stable nuclei of intermediate mass, releasing one or more neutrons. This process releases large amounts of energy. Nuclear fission is currently used in nuclear power plants.
Nuclear Fusion: The process by which light nuclei fuse to form a heavier nucleus. This process releases large amounts of energy. Fusion reactions require a lot of heat to occur, around 100,000,000 °C.
Nuclear Reactors
Nuclear reactors are systems in which the released energy is used to produce electricity. There are different types of reactors:
- Research Reactors: Use neutrons to produce isotopes.
- Power Reactors: Use heat to generate electricity.
The intensity of radiation is proportional to 1/d2, where d is the distance from the source.