This historical review traces the origins of the Kimball free-cloud model of the chemical bond, otherwise known as the charge-cloud or tangent-sphere model, and the central role it played in attempts to reform the introductory chemical curriculum at both the high school and college levels in the 1960s. It also critically evaluates the limitations…

This paper calls attention to the early work of the American chemists Worth Rodebush and Groves Cartledge, and their anticipations of a quantitative electronegativity scale, which predate the classic 1932 paper of Linus Pauling by several years. (Contains 2 figures.)

In response to a reader query, the article traces the origins of our current nomenclature and symbolism for isotopes. (Contains 2 tables.)

In response to a reader query, this article traces the history of fusible alloys, including Newton's metal, D'Arcet's metal, Rose's metal, Onion's fusible alloy, and Wood's metal. (Contains 1 table and 1 figure.)

In response to a reader query, this article traces the origins of the ionic-radius ratio rules and their incorrect attribution to Linus Pauling in the chemical literature and to Victor Goldschmidt in the geochemical literature. In actual fact, the ionic-radius ratio rules were first proposed within the context of the coordination chemistry…

The history behind the association of Avogadro's name related to the hypothesis that equal volumes of gases at constant temperature and pressure contain equal numbers of molecules is explored. The findings suggest that the index entry "Avogadro's Number" did not become common in American college texts until the 1930s and was rare in American high…

The theory of s, p, d and f dealing with the line spectra of the alkali metals during the period 1881 based on analogies with the harmonic ratios of sound is described. Friedrich Hund followed Bohr's practice of labelling the various shells and subshells by replacing the secondary quantum number with the series notations (s, p, d, and f), which…

The debate related to origin of the term "hypervalent" that was first introduced by Jeremy Musher in 1969 to describe compounds and complex ions of the heavier main-block elements in which the use of traditional Lewis 2c-2e covalent bonds requires the additional assumption of "octer expansion" for the central atom is presented. The traditional…

Benjamin Franklin first introduced the terms positive and negative into electrical theory in the year 1747. The positive and negative terms originally had nothing to do with inherent electrical charge, but rather indicated which object had an excess of electrical fluid indicating positive, and which had a deficiency, indicating negative.

A question about the historical origin of equal sign and double arrow symbolism in balanced chemical equation is raised. The study shows that Marshall proposed the symbolism in 1902, which includes the use of currently favored double barb for equilibrium reactions.

A question and answer session on whether Lavoisier made an agreement with the French mathematician, Comte Joseph-Louis Lagrange shortly before being beheaded that he would blink his eyes if he retained consciousness after being beheaded and that he was executed because of his revolutionary scientific views is described. The circumstances…

The origin of the "proof" system for measuring the ethanol content of alcoholic beverages is presented. The proof system was originally established for purposes of taxing liquors according to their alcohol content and is different in different countries.

Campbell's rule for estimating entropy changes is discussed in relation to an earlier article by Norman Craig, where it was proposed that the approximate value of the entropy of reaction was related to net moles of gas consumed or generated. It was seen that the average for Campbell's data set was lower than that for Craig's data set and…

Edward Frankland and Norman Lockyer researched upon a gaseous spectra in relation to the physical constitution of the sun and named it as "helium" (from Greek "helios" meaning "sun"). Since Lockyer apparently never formally proposed the name in print, it is not known why he chose to use a metallic end "ium".

German Chemist, August Wilhelm Hofmann first introduced the term "molar" (from the Latin moles, meaning "a large mass") into chemistry, around 1865. The particular use of the term molar gained currency in the physics literature, where it was in common use at least through the 1940s.