The Modem Periodic Table

Mendeleev was bolder in his interpretation than Lothar Meyer, and for this reason we honor him as the primary discoverer of the modem periodic table. A few elements did not fit the pattern of variation in combining numbers with molar mass. Mendeleev proposed that these irregularities meant that the element s molar mass had been measured incorrectly. For example, Mendeleev predicted that the correct molar mass of indium is 113 g /mol, not 75 g /mol, the value assigned at that time on the assumption that the formula for indium oxide is InO. Later experiments showed that the correct formula is L12 O3, and indium s tme molar mass is 114.8 g/mol. 

A family of colorless, inactive gases was unknown at the time Mendeleev conceived his periodic table. Eventually, these gases were discovered on Earth in the late 1890s. What group does this family occupy in the modem periodic table ... 

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. 

Scientists developed the modem periodic table by looking for regularities. 

The separation of elements into metals and non-metals is not clear cut and without ambiguity. The fairly obvious division between metals and non-metals is shown by a thick steeped line in the following shortened figure of the modem periodic table. Some of the elements next to the thick steps, such as germanium, arsenic and antimony have similarities to both metals and non-metals and are named... 

In the modem periodic table the elements have been arranged in the order of their increasing atomic numbers. 

E The modem periodic table is based upon atomic number, which is defined by the number of protons in the nucleus. 

In Section 1.2, we learned a few of the properties of sulfur and of iron. Do we have to learn the properties of all 100 or so elements individually, or are there some ways to ease that burden For over 140 years, chemists have arranged the elements into groups with similar chemical characteaisiics, which makes it easier to learn their properties. This grouping of the elements has been refined to a high degree, and the modem periodic table is the result. A full periodic table is shown inside the front cover of this book. The elements numbered 104 and up in that table have only recently been produced and in such infinitely small quantities that their chemical properties are unmeasured. Therefore, we will almost totally ignore them in the remainder of this book. 

In the modem periodic table, a horizontal row of elements is called a period, and a vertical column is a group or family. The traditional designations of groups in the United States differ from those used in Europe. The International Union of Pure and Applied Chemistry (lUPAC) has recommended that the groups be numbered 1 through 18, a recommendation that has generated considerable controversy. In this text, we will... 

The mass of an atom of chlorine, or any other element, is measured relative to something, just as we measure length using a standard measured metre rule. The standard has to be agreed worldwide and has to be constant, so the isotope of carbon with a mass number of 12 was chosen to be the standard, and everything is measured relative to /12 of The modem periodic table the mass of the carbon-12 isotope,... 

Research the life of a scientist, other than Mendeleev, who contribnted to the development of the modem periodic table of elements. Write a brief biography of this person and detail his or her scientific accomplishments. 

In 1869 both Mendeleev and Meyer, working separately, published nearly identical classification schemes for the elements that were the forerunners of the modem periodic table. Although scientists of that time had no knowledge of atomic numbers, both schemes ordered the elements in nearly correct order from lowest to highest atomic number. Which of the following is the most likely explanation ... 

Electron configuration determines the properties of an element. The modem periodic table classifies the elements according to their atomic numbers, and thus also by their electron configurations. The configuration of the valence electrons directly affects the properties of the atoms of the representative elements. 

The availability, only, of numerical data for the electron distributions in atoms other than hydrogen and the increasing complexity of that data with the atomic number of the atom, would be a serious limitation on our comprehension of atomic and molecular theory. In Chemistry the orbital is fundamental to the understanding of all the body of data that can be catalogued using the modem Periodic Table. It is an essential concept, too, in modem bonding theory, because general mles can be established, based on orbital interactions. 

Which statement best reflects the organization of the modem periodic table ... 

Fig. 1.13 The modem periodic table in which the elements are arranged in numerical order according to the number of protons (and electrons) they possess. The division into groups places elements with the same number of valence eleetrons into vertieal columns within the table. Under lUPAC recommendations, the groups are labelled from 1 to 18 (Arabic numbers). The vertical groups of three

As compared to the modem periodic table, the Attempted System is rotated 90° clockwise. The periods are lying vertically, rather than horizontally, and similar elements are grouped in horizontal rows, rather than vertical columns. Notice also that the rows of alkali metals and halogens are adjacent to one another (the noble gases were not yet discovered in 1869). Finally, many of the problematical elements are simply grouped on the right-hand side of the table in no particular order whatsoever. 

The modem periodic table simultaneously arranges elements in two important ways the horizontal rows of the table, called periods, and the vertical columns, called groups. The term period is used for the rows because many important... 

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