Trends in the Periodic Table

Mendeleev and Meyer developed their periodic tables by trying to organize some recurring physical and chemical properties of the elements. Some of these properties are examined in this section. 

15 Predict how first ionization energy varies with position in the periodic table. 

It takes work to remove an electron from a neutral atom. Energy must be spent to overcome the attraction between the negatively charged electron and the positively charged ion that is left. The energy required to remove one electron from a neutral gaseous atom of an element is the ionization energy of that element. 

Ionization energy is one of the more striking examples of a periodic property, particularly when graphed (Fig. 11.17). Notice the similarity of the shape of the graph between Li and Ne (Period 2 in the periodic table), between Na and Ar (Period 3), and between K and Kr (Period 4). Notice also that the peaks are elements in Group 8A/18, and the low points are from Group lA/1. 

A monatomic (one-atom) ion is an atom that has gained or lost one, two, or three electrons. If the atom loses electrons, the ion has a positive charge and is a cation if the atom gains electrons it becomes a negatively charged anion (Section 6.4). 

Similarly, as you go across a period from left to right, atoms have to lose more electrons to form stable positive ions. The more electrons have to be lost, the more energy it takes, so the harder it gets to form positive ions. In other words, as you go from left to right across a period on the left-hand side of the table, reactivity decreases. 

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Periodic Trends in the Periodic Table Use with Section 6.3... 

Another chapter (Chapter 4) is entitled Intermetallic reactivity trends in the Periodic Table . The Periodic Table, indeed (or Periodic Law or Periodic System of Chemical Elements), is acknowledged to play an indispensable role in several different sciences. Especially in inorganic chemistry it represents a fundamental classifi-catory scheme and a means of systematizing data with a clear predictive power. Inorganic chemists have traditionally made considerable use of the Periodic Table to understand the chemistry of the different elements. With a few exceptions (as detailed in the same chapter), metallurgists and intermetallic chemists have made little use of this Table to understand and describe the properties of metals and alloys we believe, however, that it may be a useful tool also in the systematics of descriptive intermetallic chemistry (as exemplified in the subsequent chapter (Chapter 5)). In several paragraphs of Chapter 4, therefore, different aspects of the Periodic Table and of its characteristic trends are summarized. 

TRENDS IN THE PERIODIC TABLE THE ROLE OF THE ATOMIC DIMENSIONS ASA FACTOR CONTROLLING THE STRUCTURE OF INTERMETALLIC PHASES... 

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