The positions of the elements La, Ac, Lu, and Lr in the WebElements periodic table is justified eloquently in the article by William B. Jensen.1
Abstract:1 The debate as to whether lanthanum and actinium or lutetium and lawrencium should be placed in group IIIB of the periodic table along with scandium and yttrium has along but poorly publicized history.
Note: Group IIIB is denoted as Group 3 today.
Elements 117 is not known at the time of writing, but are shown “greyed-out” in the tables at their expected positions for information.
WebElements December 16th, 2009
Posted In: Chemistry