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Chapter 4
The Group 3 Problem
In Chapter 3, the controversy around the placement of hydrogen (and, to a lesser extent, helium) was described. There is another controversial topic — more so, in fact — of the element choices for the two lower members of Group 3. Here, the issues will be described.
Even more contentious than the placement of hydrogen has been the membership of Group 3. The first two members are self-evident: scandium and yttrium. But which are the subsequent members of the Group? Using the long (32-column) form of the Periodic Table, there is no issue: lutetium and lawrencium fall naturally in place.
However, the 18-column form of the Periodic Table is ubiquitous. The issue becomes which set of 14 elements are pulled out and placed beneath, or whether all 15 elements are placed beneath. Is it the electron configuration or chemistry which should determine which elements occupy these positions? The debate revolved around the third member of the Group: lanthanum or lutetium, as actinium and lawrencium are highly radioactive (hence with short half-lives) and with little established chemistry. In fact, lawrencium was unknown at the time of the early discourse and actinium was assumed to be a transition metal (see Chapter 13) [1].
A History of the Debate
Jensen provided a comprehensive review of the early history of the discourse [2]. In the 1920s and 1930s, lutetium was assigned to Group 3. It was only in the 1940s that the Periodic Table was restructured according to electron configurations. At this time, lanthanum was considered to be the “legal” occupant of the “box” for Period 6, Group 3. Using arguments that will be introduced later, Jensen took the position first proposed by Luder in 1970 [3] that the correct occupants were lutetium and lawrencium, deposing lanthanum and actinium, that were sent to the rows below in the 18-group Periodic Table.
Clark and White reviewed the type of Periodic Table utilized in common U.S. textbooks over the time frame of 1948 to 2008 [4]. They identified, and provided abbreviations for, the three different 18-column Periodic Table formats (displayed in Figure 4.1).
•14CeTh. Lanthanum and actinium are placed in Group 3; the 14-member “boxes” commence with cerium (lanthanoids) and thorium (actinoids).
•14LaAc. Lutetium and lawrencium are placed in Group 3; the 14-member “boxes” commence with lanthanum (lanthanoids) and actinium (actinoids).
•15LaAc. The places in Group 3 are left vacant; the 15-member “boxes” commence with lanthanum and end with lutetium (lanthanoids), then commence with actinium and end with lawrencium (actinoids).
Clark and White showed that from 1948 up until 1984, textbooks were about evenly split between the 15LaAc and 14CeTh formats. It seems to have been Jensen’s 1982 article that led to the appearance of, and growth in, the 14LaAc format to the point where it was about an even split between 14CeTh and 14LaAc, the 15LaAc disappearing.
Figure 4.1 The three options for the members of Group 3.
At times, it has seemed less a dispute and more a case of confusion, as Jensen pointed out in 2008 [5]. He noted that the text Advanced Inorganic Chemistry by Cotton and Wilkinson used the 14CeTh format on the back flyleaf, but the 15LaAc within the text. Jensen also reported that conversely, Housecroft and Sharpe in the text Inorganic Chemistry, used the 15LaAc format on the front flyleaf but the 14CeTh format within the text.
The Dispute Becomes Heated
The years of 2008 and 2009 were busy ones for this debate. In later 2008, Lavelle came to the defense of the former arrangement, arguing that lanthanum and actinium were indeed members of the d-block elements and should remain in the body of the Periodic Table [6].
In a subsequent letter to the Journal of Chemical Education, Lavelle referred to the article by Clark and White [7]:
In their letter Clark and White wonder why the chemistry education community has not uniformly adopted just one form of the periodic table. Part of the answer is that the majority who are silent on this issue do
