Lanthanum periodic table classification

Another major classification of the elements in terms of the periodic table is shown in Figure 1.7. Three areas are defined and named the main group elements, the transition elements, and the inner transition elements. The main group elements are the simplest to learn abont, and they will be stndied first. The transition elements inclnde some of the most important elements in onr everyday lives, such as iron, nickel, chrominm, zinc, and copper. The transition elements are often divided into four rows of elements, called the first, second, third, and fourth transition series. The elements of the fourth transition series except for actinium (Ac), and those of the main group elements above 112, are artificial they are not found in nature. The two inner transition series fit into the periodic table in periods 6 and 7, right after lanthanum (La) and actinium (Ac), respectively. The inner transition elements include a few important elements, including uranium and plutonium. The first series of inner transition elements is called the lanthanide series, after lanthanum, the element that precedes... 

Under the classification of rare-earths, there are 15 lanthanide elements and the 2 elements appearing above lanthanum in the periodic table, scandium and yttrium [1]. The lanthanides are divided into two groups the first four elements are referred to as the ceric or light rare-earths, while the remaining are called the yttric or heavy rare-earths [2]. 

In fact, the classification of chemical elements is valuable only in so far as it illustrates chemical behaviour, and it is conventional to use the term transition elements in a mote restricted sense. The elements in the irmer transition series from cerium (58) to lutetium (71) are called the lanthanoids those in the series from thorium (90) to lawrencium (103) are the actl-noids. These two series together make up the /block in the periodic table. It is also common to include scandium, yttrium, and lanthanum with the lanthanoids (because of chemical similarity) and to include actinium with the actinoids. Of the remaining transition elements, it is usual to speak of three main transition series from titanium to copper from zirconium to silver and from hafnium to gold. All these elements have similar chemical properties that result from the presence of unfilled d-orbltals in the element or (in the case of copper, silver, and gold) in the ions. The elements from 104 to 109 and the undiscovered elements 110 and 111 make up a fourth transition series. The elements zinc, cadmium, and mercury have filled d-orbltals both in the elements and in compounds, and are usually regarded as nontransition elements forming group 12 of the periodic table. 

W.B. Jensen, Classification, Symmetry and the Periodic Table, Computation and Mathematics with Applications, 12B, 487-509,1986 H. Merz, K. Ukner, Position of lanthanum and lutetium in the Periodic Table, Physics Letters, 26A, 6—7, 1967 D.C. Hamilton, M.A. Jensen,... 

Interestingly, this corresponds lo modern thinking on classification of the elements contrary to the vast majority of published periodic tables in which lutetium is wrongly shown as the last of the rare earths. W. B. Jensen, The positions of Lanthanum (Actinium) and Lutetium (Lawrencium) in the Periodic Table , Journal of Chemical Education, 59 (1982), 634-6. 

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