The first metals in Mendeleiev’s Table: Part II. A new argument against the placement of hydrogen atop the alkali metal column

Abstract

Every so often an experiment trying to give reliable evidence for a metallic hydrogen solid is reported. Such evidence is, however, not too convincing. As Eric Scerri has recently reiterated, “the jury is still out on that issue” (Scerri 2012). This search stems from the common spectroscopy shared by the hydrogen atom and all the alkali metal atoms, and perhaps is guided by a desire to place hydrogen atop the alkali metals, in Mendeleiev’s Table, reinforced by the fact pointed out by Scerri (The Periodic Table, its story and its significance, Oxford University Press, Oxford, 2007, 2012) that there is no other obvious place for hydrogen in said Table. But H₂ is a light gas at room temperature, while Li, Na, K and the other alkali elements form solid metal crystals. At very low temperatures, of course, hydrogen solidifies, but it is formed by H₂ molecules (see for example, Van Kranendonk in Solid hydrogen, Plenum Press, New York, 1983). Our purpose here is to use a new argument to break this impasse: “should H be grouped with the alkali metals with which it shares a common spectroscopy, but which solidifies in a completely different fashion?” This argument has been proposed before in a couple of papers in this journal to establish a similar question for He and the alkaline earths (Novaro in Found Chem 10:4, 2008, Ramírez-Solís and Novaro in Found Chem, 2012), as is discussed in “Precedents” section.