Understanding Chemical Laws: Proust, Dalton, Richter & Radioactivity
Understanding Key Chemical Laws
Law of Definite Proportions (Proust’s Law)
Joseph Louis Proust (1754-1826) argued that the percentage composition of a chemical compound was always the same, regardless of origin. In contrast, Claude Louis Berthollet (1748-1822) stated that elements, within certain limits, could join in all proportions.
Over time, Proust’s criterion was supported by an experiment conducted in 1799, showing that the composition of cupric carbonate was always the same, regardless of its method of production in nature or in the laboratory: 5 parts of copper, four of oxygen, and one of carbon.
Therefore: elements combine to form compounds, and they always do so in fixed and defined proportions.
Law of Multiple Proportions (Dalton’s Law)
Subsequent investigations carried out to determine the proportions in which chemical elements combine sometimes showed apparent contradictions with Proust’s Law, because chemical elements sometimes combine in more than one proportion. For example, 1 g of nitrogen can be combined with three different ratios of oxygen to provide three different nitrogen oxides.
Law of Reciprocal Proportions (Richter’s Law)
The generalization of this to other examples has led to the enunciation of the Law of Reciprocal Proportions as follows: the masses of the elements that combine with a body of a third party bear the same proportion as the masses when the two combine together.
Law of Conservation of Mass (Lavoisier’s Law)
Lavoisier proved his law in many reactions, most of which consisted of subjecting various metals to heating in sealed containers with a certain amount of air, but, above all, by measuring the masses of the substances before and after the reaction. These experiments led him not only to verify that the oxygen in the air combines with metals during the oxidation reaction but also to show the conservation of mass during the process.
Radioactivity
Radioactivity is a natural physical phenomenon by which certain bodies or chemical elements, called radioactive, emit radiation that has the property to impress photographic plates, ionize gases, produce fluorescence, and pass through opaque materials. Because of this capability, it is often referred to as ionizing radiation (in contrast to non-ionizing radiation). The electromagnetic radiation may be emitted in the form of X-rays or gamma rays or corpuscular, such as helium nuclei, electrons or positrons, protons, or other particles. In short, it is a phenomenon that occurs in the nuclei of certain elements, which are capable of becoming core elements of other atoms.
Radioactivity is a property of isotopes that are “unstable.” They are kept in an excited state in their electronic and nuclear layers, so to reach their ground state, they must lose energy. They do this through electromagnetic or particulate emissions with a certain kinetic energy. This occurs by varying the energy of its electrons (emitting X-rays), its nucleons (gamma rays), or varying the isotope (the output from the core electrons, positrons, neutrons, protons, or heavier particles), and in several steps, a heavy isotope can develop into a much lighter one, such as uranium, which, with the passing of centuries, becomes lead.
It is exploited for obtaining energy, used in medicine (radiotherapy and radiology), and industrial applications (measurements of thickness and density, among others).
Radioactivity can be:
- Natural: shown by the isotopes found in nature.
- Artificial or induced: manifested by radioisotopes produced in artificial transformations.