In the last decade, the notion of triad was reintroduced by Eric Scerri, who suggested it as a possible categorical criterion to represent chemical periodicity. In particular, he reformulated the notion of triad in terms of atomic number instead of atomic weights; in this way, the value of the intermediate term of the triad became the exact average of the values of the two extremes. Following the inspiration of Scerri’s work, the main purpose of this article is to obtain a (...) representation where all the relations among the chemical elements that form the groups of the periodic system can be reconstructed on the basis of triads, without using electronic configurations. (shrink)

Several attempts have recently been made to point to ‘the proper place’ for hydrogen in the Periodic Table of the elements. There are altogether five different types of arguments that lead to the following conclusions: hydrogen should be placed in group 1, above lithium; hydrogen should be placed in group 17, above fluorine; hydrogen is to be placed in group 14, above carbon; hydrogen should be positioned above both lithium and fluorine and hydrogen should be treated as a stand-alone element, (...) in the center of the Periodic Table. Although all proposals are based on arguments, not all of them sound equally convincing. An attempt is made, after critical reexamination of the arguments offered, to hopefully point to the best possible choice for the position of hydrogen. A few words are also mentioned on the structure of the Periodic Table and the attempts to reorganize it. (shrink)

A large variety of periodic tables of the chemical elements have been proposed. It was Mendeleev who proposed a periodic table based on the extensive periodic law and predicted a number of unknown elements at that time. The periodic table currently used worldwide is of a long form pioneered by Werner in 1905. As the first topic, we describe the work of Pfeiffer, who refined Werner’s work and rearranged the rare-earth elements in a separate table below the main table for (...) convenience. Today’s widely used periodic table essentially inherits Pfeiffer’s arrangements. Although long-form tables more precisely represent electron orbitals around a nucleus, they lose some of the features of Mendeleev’s short-form table to express similarities of chemical properties of elements when forming compounds. As the second topic, we compare various three-dimensional helical periodic tables that resolve some of the shortcomings of the long-form periodic tables in this respect. In particular, we explain how the 3D periodic table “Elementouch”, which combines the s- and p-blocks into one tube, can recover features of Mendeleev’s periodic law. Finally we introduce a topic on the recently proposed nuclear periodic table based on the proton magic numbers. Here, the nuclear shell structure leads to a new arrangement of the elements with the proton magic-number nuclei treated like noble-gas atoms. We show that the resulting alignments of the elements in both the atomic and nuclear periodic tables are common over about two thirds of the tables because of a fortuitous coincidence in their magic numbers. (shrink)

In April 2015, an international team of researchers announced the measurement, for the first time, of the first ionization energy of lawrencium, a superheavy element of atomic number 103. The experimental result, published in the prestigious scientific journal Nature, led to the reopening of a long-standing debate that concerns the elements that should be part of group 3 of the periodic table. The aim of this paper is to introduce a new line of argumentation to elucidate this problem.

How do we teach chemistry as a different science from physics? This paper looks into a fundamental distinguishing property of chemistry as a science. It is characterized in this paper that chemistry, unlike many other sciences that are largely descriptive, is primarily creative. In this sense, the various fields of chemistry may seek to create as an end goal, and not merely to create as a means to an end as commonly seen in allied sciences. This distinction is important as (...) it elevates the importance of chemical synthesis above being a small detail of the field. I argue in this paper that synthesis is a largely defining character of chemistry as a structured science, and must be given importance to when attempting to define chemistry as a separate study from similar fields. Awareness of the importance of synthesis can elucidate on the manner and trends of normal chemical research as well as predict possible circumstances that will arise for the field of chemistry. (shrink)