Potassium is the main intracellular ion in prokaryotic and eukaryotic cells and is essential for their functions, making potassium one of the most important electrolytes in physiology. In humans, potassium plays a vital role in several physiological functions, including the maintenance of fluid balance, generating the membrane potential of cells,…

The formulation of the periodic system by the Russian Mendeleev was followed by the surprising discovery of gallium by the Frenchman de Boisbaudran. The Englishman Ramsay's explanation of an 'impurity' in air led to recognition of a new period. A young fellow countryman, Moseley, justified the expected existence of 92 elements. A German couple,…

This article looks at the events that led to the discovery of isotopes in the early part of the 20th century. It is difficult to claim that the discovery was a single event. A number of famous scientists worked independently to provide the evidence, and the understanding of the need to think differently about atoms gradually emerged. Four varied…

The Earth's primary atmosphere, which was similar to that of the gas giant planets, was soon lost, and a secondary atmosphere was established by outgassing from the early Earth and from colliding debris. The composition of this atmosphere was probably similar to present-day volcanic emissions but with a tiny percentage of photochemically produced…

The nature of light and how it is affected by gravity is discussed. Einstein's prediction of the deflection of light as it passes near the Sun was verified by observations made during the solar eclipse of 1919. Another prediction was that of gravitational redshift, which occurs when light emitted by a star loses energy in the gravitational field…

Accidental discoveries have been of significant value in the progress of science. Although accidental discoveries are more common in pharmacology and chemistry, other branches of science have also benefited from such discoveries. While most discoveries are the result of persistent research, famous accidental discoveries provide a fascinating…

Discusses the historical background of the development of lightning conductors, describes the nature of thunderclouds and the lightning flash, and provides a calculation of the electric field under a thundercloud. Also discussed are point discharge currents and the attraction theory of the lightning conductor. (JR)

Describes the development of vaccination and provides a brief biographical sketch of the life and work of Pasteur. Describes historical practices related to vaccination before Pasteur did his work, including variolation as practiced by the ancient Chinese and Jenner's use of smallpox. (PR)

Describes how some of the Theory of Knowledge (ToK) requirements, which is a central part of the International Baccalaurate (IB) Diploma program, for the natural sciences component can be addressed through case studies from the history of chemistry and related subjects. Provides examples for the 'Ideas and evidence in science' which can be useful…

Discusses pollution in medieval times, focusing on pollution related to: (1) wood; (2) coal; (3) tanning; and (4) lead. (JN)

Provides background information for teachers on the chemistry of flourine. Points out that it links aerosols with refrigerants, anaesthetics with fire-fighting agents, batteries with blood substitutes, and atomic energy with the steel, petroleum, and aluminum industries. (JN)