Nobel Laureates in Chemistry: Chromatography, Radioactivity, and Ionic Dissociation
Nobel Laureates in Chemistry: Key Discoveries
Archer John Martin and Richard Laurence Millington Synge
Millington Synge: Awarded the 1952 Nobel Prize for Chemistry for their contribution to the knowledge of techniques of substance analysis, specifically in chromatography.
Chromatography is an analytical technique used to identify and separate the components of a mixture. It is based on the selective interaction of pigments with an adsorbent material. Different adsorbents are used to separate compounds that can mix together, even hundreds of different substances.
Chromatographic separation is achieved by distributing the components of a mixture between a fixed or stationary phase and a mobile phase. Separation begins when one of the substances is retained more strongly by the stationary phase than the others.
The fixed or stationary phase can be a solid with a large surface area that acts as a support for the process. The mobile phase is a fluid that carries the mixture across the stationary phase.
Two Major Events in Chromatography:
- Adsorption: Surface retention of a substance on the chemical surface of a solid. This retention depends on the nature of the substance, temperature, and the concentration of the adsorbent substance.
- Absorption: The retention of a chemical species by a fluid. This retention depends on the tendency of the species to react chemically with the fluid.
Marie Curie
Awarded a Nobel Prize in Chemistry for her work on radioactivity. This phenomenon had been previously studied by Ernest Rutherford, who identified three types of radiation using an electric field: alpha, beta, and gamma.
Radioactivity
Radioactivity is the emission of rays or particles from the unstable nucleus of an atom. This radiation stabilizes the atom. Many radioactive atoms are classified in the periodic table with atomic numbers greater than or equal to 83.
Unstable atoms are classified as:
- Isotopes: Atoms with the same atomic number but different mass numbers (e.g., nitrogen and carbon). Z: Atomic Number, A: Mass Number
- Isobars: Atoms with the same mass number but different atomic numbers (e.g., mercury and lead).
- Isotones: Atoms with the same number of neutrons but different atomic numbers. Z = e
Characteristics of Radioactive Particles:
- Alpha Particles: Positively charged particles with a charge of +2 and a mass of 4 on the atomic weight scale.
- Beta Particles: Have the properties of electrons. They are abbreviated as E1 B-1B and are much smaller than alpha particles. They have medium penetration and can pass through paper but not aluminum foil.
- Gamma Radiation: High-energy electromagnetic radiation. It has neither mass nor charge, so we cannot speak of gamma particles. It can cross matter and is only stopped by a lead plate of about 7 mm.
Svante Arrhenius
Theory of Ionic Dissociation
Arrhenius Equation
Concept of pH
Theory of Ionic Dissociation
Nobel Prize 1903: At that time, it was thought that ions were formed only by the passage of electric current. Arrhenius established that in some cases, ions exist in a solid state and dissociate when these solids are placed in H2O, as with NaCl. Arrhenius observed that even some aqueous solutions that are not liquids conduct electricity, such as HCl, because when dissolved in H2O, it forms ions and can conduct electricity.
Through experiments with batteries, water, sodium, and sodium chloride, Arrhenius called substances that conduct electricity electrolytes and those that do not non-electrolytes. Non-electrolytes remain in molecular form in aqueous solution, while electrolytes exist in ionic form.
A group of scientists improved Arrhenius’s assembly by incorporating a bulb to determine if an electrolyte was strong or weak, depending on the intensity with which the bulb lit up.