Periodic table origin

These elements formed Group IIB of Mendeleef s original periodic table. As we have seen in Chapter 13, zinc does not show very marked transition-metaf characteristics. The other two elements in this group, cadmium and mercury, lie at the ends of the second and third transition series (Y-Cd, La-Hg) and, although they resemble zinc in some respects in showing a predominantly - - 2 oxidation state, they also show rather more transition-metal characteristics. Additionally, mercury has characteristics, some of which relate it quite closely to its immediate predecessors in the third transition series, platinum and gold, and some of which are decidedly peculiar to mercury. 

When Mendeleev invented the periodic table, he was well-acquainted with Dalton s atomic theory. He knew nothing, however, about subatomic particles, and especially the electron, which is the foundation for the modern periodic table s distinctive shape. Because the original periodic table developed out of experimental observations, chemists did not need an understanding of atomic structure to develop it. (As you will see in section 3.3, however, the periodic table easily accommodates details about atomic structure. In fact, you will learn that the modern periodic table s distinctive design is a natural consequence of atomic structure.)... 

The chemical behavior of the transuranium elements is interesting because of its complexity and the insights offered into the chemistry of the lighter elements. The placing of these manmade elements into the periodic table (Fig. 15.1) represents one of the few significant alterations of the original periodic table of Mendelyeev. Since so little is known about the chemistry of the transactinide elements, one has the unique opportunity to test periodic table predictions of chemical behavior before the relevant experiments are done. 

When Mendeleev produced his original Periodic Table in 1869, he left a space for a metallic element of atomic mass 44 preceding yttrium. The first fairly pure scandium compounds were isolated by Cleve in 1879, but it was not until 1937 that the element itself was isolated. Although a relatively abundant element, it is fairly evenly distributed in the earth s crust and has no important ores, though it is the main component of the rare ore thortveitite (Sc2Si207), thus being relatively expensive. In fact, it is mainly obtained as a by-product from uranium extraction. 

Figure 9.1 Mendeleev s original periodic table (1869). The elements in the gaps marked with red squares— now known to be Sc, Ga and Ge—were predicted by Mendeleev before they were actually discovered.

Mendeleev s original periodic table contained only about 60 elements. That was the total number of elements known in 1869. When he drew his first periodic table, Mendeleev found some empty places. What did those empty places mean ... 

Mendeleev arranged the elements in his original periodic table in order of increasing atomic mass. However, as our knowledge of atomic structure increased, atomic numbers became the basis for the organization of the table. 

Mendeleevs original periodic table is remarkable given the knowledge of elements at that time, and yet it is different from the modern version. Compare Mendeleevs table, shown in Table 6.12, with the modern periodic table shown in Figure 6.5. 

By the seventeenth century, the common strong acids— nitric, sulfuric, and hydrochloric—were known, and systematic descriptions of common salts and their reactions were being accumulated. As experimental techniques improved, the quantitative study of chemical reactions and the properties of gases became more common, atomic and molecular weights were determined more accurately, and the groundwork was laid for what later became the periodic table of the elements. By 1869, the concepts of atoms and molecules were well established, and it was possible for Mendeleev and Meyer to propose different forms of the periodic table. Figure 1.9 illustrates Mendeleev s original periodic table. ... 

Dimitri Mendeleev s Original Periodic Table (and other tables) http //chemlab.pc.maricopa.edu/periodic/foldedtable.htmi... 

The original periodic table. In 1870, the Russian chemist Dmitri Mendeleev arranged the 65 elements known at the time into a table and sununarized their behavior in the periodic law when arranged by atomic mass, the elements exhibit a periodic recurrence of similar properties. Mendeleev left blank spaces in his table and was even able to predict the properties of several elements, for example, germanium, that were not discovered until later. 

This discovery completed the sequence of 14 elements occurring between the atomic numbers 58 and 71 inclusive. The group did not fit into the original periodic tables and was included as the separate lanthanide series . Lanthanum itself, together with two other group 3A elements, yttrium and scandium (and sometimes thorium), is often included with the lanthanide series elements in discussions of the REE. This is because they frequently occur together in rare earth minerals, having similarities in ionic radii and chemical activity. 

Despite the proliferation of the ways of representing the chemical periods, the simple block structure dominates schoolrooms and boardrooms ahke, serving along with the test-tube and the beaker as a universal symbol of chemistry. In constructing the original periodic table which dates... 

A Mendeleev s arrangement of the elements in the original periodic table was based on observed chemical and physical properties of the elements and their compounds. The arrangement of the elements in the modern periodic table is based on atomic properties—atomic number and electron configuration. 

In this oxidation state the titanium atom has formally lost its 3d and 4s electrons as expected, therefore, it forms compounds which do not have the characteristics of transition metal compounds, and which indeed show strong resemblances to the corresponding compounds of the lower elements (Si, Ge, Sn, Pb) of Group IV—the group into which Mendeleef put titanium in his original form of the periodic table. 

Originally this resource, the Periodic Table, was created by Robert Husted at Los Alamos National Laboratory during his time as a Graduate Research Assistant. 

Lead, atomic number 82, is a member of Group 14 (IVA) of the Periodic Table. Ordinary lead is bluish grey and is a mixture of isotopes of mass number 204 (15%), 206 (23.6%), 207 (22.6%), and 208 (52.3%). The average atomic weight of lead from different origins may vary as much as 0.04 units. The stable isotopes are products of decay of three naturally radioactive elements (see Radioactivity, natural) comes from the uranium series (see Uraniumand... 

While still a student at the Academy, Ipatieffbegan to make a name for himself in the Russian chemical community as he began to publish some of his laboratory findings. His first professional milestone as a chemist came in 18h() when he joined Russia s Physical-Chemical Society. Here he came into close contact with Russia s most famous chemists, including Dimitri Mendeleev, discoverer of the periodic table and one of the founders ol the Society. In 1891, upon graduating from the school, he was appointed lecturer in chemistry at the Academy where he also continued to undertake original chemical research for his doctoral dissertation. In 1895, he was made assistant professor and, upon completion and acceptance of his dissertation in 1899, he became a full professor of chemistry. 

But alas most of what has been described so far concerning density theory applies in theory rather than in practice. The fact that the Thomas-Fermi method is capable of yielding a universal solution for all atoms in the periodic table is a potentially attractive feature but is generally not realized in practice. The attempts to implement the ideas originally due to Thomas and Fermi have not quite materialized. This has meant a return to the need to solve a number of equations separately for each individual atom as one does in the Hartree-Fock method and other ab initio methods using atomic orbitals. 

So if one selects any element at random there is a 50% chance that the element above and below the selected element, in the same column of the periodic table, will have atomic numbers at an equal interval away from the original element. If this is the case, then it follows trivially that the second element in the sequence will lie exactly mid-way between the first and third elements. In numerical terms, its atomic number will be the exact mean of the first and third elements, or in other words the atomic number triad will hold perfectly. All one needs to do is to pick a middle element from the first of a repeating pair of periods. Thus about half of all the elements are good candidates for beginning a triad. This phenomenon is therefore a mathematical consequence of the fact that all periods repeat (except for the first one) and that the elements are characterized by whole number integers. 

This form of the periodic table is shown in Figure 1. Although it is often assumed to have a quantum mechanical origin it was first proposed on purely esthetic grounds by the Frenchman, Charles Janet [23]. But in a quantum mechanical guise it takes on a new lease of life, as will be explained shortly. 

This chapter builds an understanding of atomic structure in four steps. First, we review the experiments that led to our current nuclear model of the atom and see how spectroscopy reveals information about the arrangement of electrons around the nucleus. Then we describe the experiments that led to the replacement of classical mechanics by quantum mechanics, introduce some of its central features, and illustrate them by considering a very simple system. Next, we apply those ideas to the simplest atom of all, the hydrogen atom. Finally, we extend these concepts to the atoms of all the elements of the periodic table and see the origin of the periodicity of the elements. 

The Origin of the Relativistic Maximum at Cold Along the 6th Period of Elements in the Periodic Table... 

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