Periodic Table long-form

Flgore 9.10 A modem periodic table (long form)... 

There is no single best form of the periodic table since the choice depends on the purpose for which the table is used. Some forms emphasize chemical relations and valence, whereas others stress the electronic configuration of the elements or the dependence of the periods on the shells and subshells of the atomic structure. The most convenient form for our purpose is the so-called long form with separate panels for the lanthanide and actinide elements (see inside front cover). There has been a lively debate during the past decade as to the best numbering system to be used for the individual... 

Organic chemistry, then, is the study of carbon compounds. But why is carbon special Why, of the more than 30 million presently known chemical compounds, do more than 99% of them contain carbon The answers to these questions come from carbon s electronic structure and its consequent position in the periodic table (Figure 1.1). As a group 4A element, carbon can share four valence electrons and form four strong covalent bonds. Furthermore, carbon atoms can bond to one another, forming long chains and rings. Carbon, alone of all elements, is able to form an immense diversity of compounds, from the... 

Figure 7. In the conventional medium-long form of the periodic table, the elements axe shown with the 4-block (pink) between the s-block (blue) and the p-block (lavender), to reflect the order of subshell tilting shown in figure 10 and contrary to the order expected from figure 6.

Alternatively any triads taken from combinations of elements in rows 2, 3, 4 or 4, 5, 6 and so on, do not give perfect triads. The reason why this works so perfectly, albeit in only about 50% of possible triads, is because the length of each period repeats just once in the long-form periodic table, with the exception of the very first short period. The full sequence is 2, 8, 8, 18, 18, 32, presumably 32, and so forth. 

Consequently, they maintain that some displays of the periodic system may, in truth, be superior to others. Whereas the conventionally displayed table, called the medium-long form, has many virtues, it places helium among the noble-gas elements. Some have argued that in spite of appearances, helium should in fact be placed el the head of group 2, the alkaline earth group, which includes beryllium, magnesium and calcium. Helium has two outer-shell electrons as do the elements in the alkaline earth group. 

FIGURE 2. Medium-long form periodic table. 

FIGURE 5. Long-form periodic table highlighting several atomic number triads. 

The problem is no longer the validity of Mendeleev s system, but the best way to represent it. Should it be the original short-form table with 8 columns, the familiar medium-long form with 18 columns, or perhaps even a long-form table with 32 columns, which more naturally accommodates the rare earth elements Into the main body of the table Altanahvely, some favor pyramidal tables, while others advocate the left-step form proposed by diaries Janet in the 1920s. Theodor Benfey and rhilip Stewart have proposed continuous spiral models. Hundreds, possibly even thousands, of periodic systems have been proposed, and each has its ardent supporters. 

Is there one best periodic table Many chemists argue that the form of the table is of little importance and that one s choice depends on what particubr aspect of periodicity one wants to depict. But surely this is not the case if. for example, rival versions put helium and hydrogen in radically different places. Such debates will continue for a long time. However, the debate would not exist without Dmitri Ivanovich Mendeleev, and for the very legacy of periodicity we are indebted to him. 

The actinoid elements (or actinides An) constitute a series of 14 elements which are formed by the progressive filling of the 5/ electron shell and follow actinium in the periodic table (atomic numbers 90-103). All of the isotopes of the actinide elements are radioactive and only four of the primordial isotopes, Th, and " " Pu, have a sufficient long half-life for there to be any of these left in nature. 

Fig. 2.2. The periodic table of chemical elements, displayed in the modem long form. Each element is denoted by its symbol. From U (element atomic number 92) the elements have been...

The long form of the periodic table, with the four energy suhlevel blocks identified. 

Bonds between C s are covalent and strong, so that C s can form long chains and rings, both of which may have branches. C s can bond to almost every element in the periodic table. Also, the number of isomers increases as the organic molecules become more complex. 

Copper is one of the more abundant elements in the earth s crust (68 p.p.m.) it is about 20th in the order of abundance, occurring at a concentration of about 100 g per ton of the earth s crust.1 It occurs in group lb of the Mendeleev form of the periodic table (Table la),2 or alternatively in the first-row transition metals (Ni, Cu, Zn) in the long form of the periodic table (Table lb),3 or in group lid in the new long form of the periodic table (Table lc) recently proposed by the American Chemical Society.4... 

Table 1 The Three Notations of the Periodic Table (a) the Mendeleev Form, (b) the Long Form and (c) the New...

A quick look in the periodic table reveals that the rare earths in a very unsophisticated way are grouped together with the members of group III b. In the conventional long form of the periodic table La is classified with Sc and Y. A number of writers [176,177] have questioned this classification and are more inclined to include Lu (instead of La) in the same column as Sc and Y. There are logical arguments in support of each of these points of view. Here we have no intention to evaluate the relative merits of these arguments. 

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