The location and composition of Group 3 of the periodic table

Abstract

Group 3 as Sc–Y–La, rather than Sc–Y–Lu, dominates the literature. The history of this situation, including involvement by the IUPAC, is summarised. I step back from the minutiae of physical, chemical, and electronic properties and explore considerations of regularity and symmetry, natural kinds, and quantum mechanics, finding these to be inconclusive. Continuing the theme, a series of ten interlocking arguments, in the context of a chemistry-based periodic table, are presented in support of lanthanum in Group 3. In so doing, I seek to demonstrate a new way of thinking about this matter. The last of my ten arguments is recast as a twenty-word categorical philosophical (viewpoint-based) statement.

Understanding Periodic and Non-periodic Chemistry in Periodic Tables

“…elements, and Y can be related to the heavy group-3 (La, Ac) or group-3' (Lu, Lr) elements (see also Figure 4 ). While active chemists usually investigate the comprehensive group, there are authors who prefer to classify the border-case elements in a rigorous unique manner (Luchinskii and Trifonov, 1981 ; Jensen, 1982 , 2003 , 2015 ; Grochala, 2018 ; Petruševski and Cvetković, 2018 ; Chandrasekara et al, 2019 ; Kurushkin, 2020 ; Rayner-Canham, 2020 ; Scerri, 2020 ; Vernon, 2020b ). Anyhow, the bifurcations in the Periodic System are a basic aspect of empirical chemical periodicity (Bayley, 1882 ; Carnelley, 1886 ; Thomsen, 1895 ; Bohr, 1922 ; Hackh, 1924 ; Von Antropoff, 1926 ; Clark, 1933 , 1950 ; Shchukarev, 1954 ).…”

“…How to define the f-block (i.e., including, or not, lanthanum and actinium or lutetium and lawrencium, or both pairs) within the series of early d-block elements is a still ongoing, standpoint-oriented controversy of philosophical, though of little chemical relevance (Edelstein et al, 2010 ; Morss et al, 2010 ; Pyykkö, 2019 ; Vernon, 2020b ). Covalent contributions to the bonds of all these elements are dominantly based on the ( n −1)d orbital overlap interactions.…”

On the singularity of scandium

“…The 150th anniversary in 2019 of Mendeleev's first description of a periodic table of the elements has reawakened interest in the contemporary version of the Periodic Table, including the question of which element should be grouped with scandium and yttrium in Group 3. [1][2][3][4][5][6] In fact, scandium has an ambivalent position in the Periodic Table, in that it both 'looks south' in Group 3 and also 'looks east' to the remaining 3d metals. Until the recent discovery of important applications in new materials leading to its description as the ''miracle metal'' 7 and to the US Government's inclusion of scandium ores on its list of ''critical minerals'', 8 scandium was long-regarded as little more than a chemical oddity, largely because of the seemingly uninteresting nature of its basic solution chemistry.…”

Assessment of the Second-Ionization Potential of Lawrencium: Investigating the End of the Actinide Series with a One-Atom-at-a-Time Gas-Phase Ion Chemistry Technique

“…The question is whether or not Lu and Lr, should terminate the 4f and 5f blocks, concluding the lanthanide and actinide series, respectively [7]. Or, if Lu and Lr should instead be considered as group 3 elements to initiate the 5d and 6d series, respectively [8]. This proposed arrangement would modify Seaborg's Actinide Hypothesis put forth in the 1940's, which declared that the actinide series should end with element 103, Lr [9,10].…”

“…Presently, there is much discussion on the accurate placement of the elements Lu ( Z = 71) and Lr ( Z = 103) . The question is whether or not Lu and Lr should terminate the 4f and 5f blocks, concluding the lanthanide and actinide series, respectively; or, if Lu and Lr should instead be considered as group 3 elements to initiate the 5d and 6d series, respectively . This proposed arrangement would modify Seaborg’s actinide hypothesis put forth in the 1940’s, which declared that the actinide series should end with element 103, Lr. , Seaborg had declared that the actinide series was completed with the discovery of Lr in 1961 .…”