The Modern Periodic Table

Periodic table Arrangement of elements in atomic number order in rows so that elements with similar properties fall together in vertical columns 

Groups Vertical columns of elements with similar properties in the periodic 

Representative or main-group elements Elements in the A groups of the periodic table 

Transition elements Elements in periodic table rows 4-7 in which dor f orbitals are being filled they lie between main-group elements 

Inner transition eiements Elements 58-71 (lanthanides) and 90-103 (actinides), which lie between Groups 2A and 3A of the main group elements and are usually placed at the bottom of the periodic table 

The modern periodic table appeared as a function of the physical and chemical properties of elements. When the elements are arranged in the order of increasing atomic numbers, there is a periodic repetition in the properties of these elements. 

A simple periodic table contains the symbols, atomic numbers and the relative atomic masses of the elements. Additionally, detailed periodic tables containing some physical and chemical properties (such as melting point, boiling point, oxidation state) are also made. 

You can find more information about the elements in Appendix C. 

The physical and chemical properties of the elements are directly related to their electron configurations. For example, chemical properties such as gaining, giving and sharing of electrons are dependent on the valence electrons and nucleus structure. As a result, chemical behaviors of the elements are closely related to the nucleus structure and electron configuration of the element. Elements in the same period contain different numbers of electrons in the valence shells. 

For this reason, elements in the same period have different physical and chemical properties. 

Elements in the modern periodic table are arranged sequentially by atomic number in rows and columns. Mendeleev and his contemporaries arranged elements according to atomic mass. In 1913, Henry Moseley s (1887-1915) studies on the x-ray diffraction patterns for metals showed a relationship between the spectral lines and the atom s nuclear charge. Moseley s work established the concept of atomic number, the number of protons in the nucleus, as the key for determining an element s position in the periodic table. Rows in the periodic table 

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Reference to the modern periodic table (p. (/)) shows that we have now completed the first three periods—the so-called short periods. But we should note that the n = 3 quantum level can still accommodate 10 more electrons. 

Chemical properties and spectroscopic data support the view that in the elements rubidium to xenon, atomic numbers 37-54, the 5s, 4d 5p levels fill up. This is best seen by reference to the modern periodic table p. (i). Note that at the end of the fifth period the n = 4 quantum level contains 18 electrons but still has a vacant set of 4/ orbitals. 

Moreover, if we consider atomic numbers instead of atomic weights for the triads discovered in Ihe 19th century, it turns out that the atomic number of Ihe middle element is exactly the average vt the other two elements Indeed, about halt of al Ihe possible triads in the modern periodic table are exact in this sense However many other potential triads are not even approximately correct in that the atomic number of the middle dement is nowhere near Ihe average of Ihe other two... 

The modern periodic table has elements arranged in order of increasing atomic number so that elements with similar chemical properties fall in the same column. 

In the modern periodic table, horizontal rows are known as periods, and are labeled with Arabic numerals. These correspond to the principal quantum numbers described in the previous section. Because the outer shells of the elements H and He are 5 rather than p orbitals, these elements are usually considered differently from those in the rest of the table, and thus the 1st period consists of the elements Li, Be, B, C, N, O, F, and Ne, and the 2nd Na to Ar. Periods 1 and 2 are known as short periods, because they contain only eight elements. From the discussion above, it can be seen that these periods correspond to the filling of the p orbitals (the 2p levels for the first period, and the 3p for the second), and they are consequently referred to as p-block elements. The 3rd and 4th periods are extended by an additional series of elements inserted after the second member of the period (Ca and Sr respectively), consisting of an extra ten elements (Sc to Zn in period 3 and Y... 

The modern periodic table represents a pinnacle of the achievement of many nineteenth- and twentieth-century chemists, and is a clear visual expression of our understanding of the structure of the atom. It is not only beautiful, however - it is also supremely useful. It offers a simple key to predicting a wealth of physical and chemical data about the elements and their compounds. It is possible to predict the properties and behavior (biogeochemically, as well as chemically) of hundreds of compounds, from a knowledge of a few. It is the key to understanding modern chemistry. 

Know how the modern periodic table was developed, including the differences between Mendeleev s table and the current table. 

As you know, Dalton s atomic theory no longer applies in its original form, and Mendeleev s periodic table has undergone many changes. For example, scientists later discovered that atoms are not the most basic unit of matter because they are divisible. As well, the modern periodic table lists the elements in order of their atomic number, not their atomic mass. Of course, it also includes elements that had not been discovered in Mendeleev s time. Even so, in modified form, both of these inventions are still studied and used today in every chemistry course around the world. 

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.)... 

However, Mendeleev received credit for devising the modern periodic table of the elements, even though his table was based on atomic mass numbers rather than the atomic proton numbers of the elements. In 1871 he arranged the elements not only by their atomic mass in horizontal rows (periods), but also in vertical columns (groups, also called families) by their valences as well as other chemical and physical characteristics. 

In the modern periodic table, each box contains four data, as shown in Figure 1-2. Besides the element name and symbol, the atomic weight is at the bottom, and the atomic number is at the top. The elements are arranged in order of increasing atomic number in horizontal rows called periods. 

If there were a flag that represented the science of chemistry, it would be the periodic table. The periodic table is a concise organizational chart of the elements. The periodic table not only summarizes important facts about the elements, but it also incorporates a theoretical framework for understanding the relationships between elements. The modern periodic table attests to human s search for order and patterns in nature. As such, the periodic table is a dynamic blueprint for the basic building blocks of our universe. This chapter examines the development of the modern periodic table and presents information on how the modem periodic table is organized. 

The second development that led to the modern periodic table was the acceptance of specific atomic masses for the elements. While today we readily accept the masses given in a periodic table, there was much... 

Despite Meyer s efforts, Mendeleev receives the majority of credit for the modern periodic table. Mendeleev s table resulted from years of work examining the properties of the elements. Mendeleev s method involved writing information about the elements on individual cards and then trying to organize the cards in a logical order. His genius resulted from modifications he introduced into his table that others had not included. He produced his table in... 

The modern Periodic Table of elements. The numbers indicate the atomic number of each element the number of protons its nucleus contains. Some superheavy elements beyond meitnerium (Mt) have been observed but not yet named... 

In his table, Mendeleyev arranged the elements according to atomic mass, leaving spaces for the elements that were not yet known. Carbon was placed in the sixth position. The modern periodic table is organized differently. While today we know that Mendeleyev made a few mistakes, carbon still remains in the sixth position. 

The elements in the modern periodic table are arranged according to atomic number, the number of protons in the atom. 

Dmitri Mendeleyev (1834-1907), a Russian scientist and creator of the modern periodic table, discovered that if elements were lined up according to atomic weights and arranged in rows of 2, 8, 18, and 32, atoms with similar chemical and physical properties appeared in the same column. However, there were some exceptions. Argon and potassium were out of place. So were iodine and tellurium. Mendeleyev thought his relative weights were incorrect. 

The Modern Periodic Table Order from Chaos... 

The modern periodic table provides us with volumes of information about the elements. Metals are on the left side of the table, nonmetals are on the right side, and metalloids divide these two groups. In general, metals are shiny, malleable, ductile, and conduct electricity. Nonmetals are dull, brittle, and do not conduct electricity (many nonmetals are gases at room temperature). Metalloids have properties of both metals and nonmetals. 

Dmitri Mendeleev is often considered the father of the periodic table, and the studies of many scientists have also contributed to form the modern periodic table. 

Moseley determined the number of protons (atomic numbers) of the elements by the wavelength of X-rays emitted by atoms which were bombarded by electrons. He claimed that the elements in the periodic table must be arranged according to their atomic numbers instead of their atomic masses. Thus, the modern periodic table appeared. 

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