Nonmetals periodic trends

What Do We Need to Know Already It would be a good idea to review the information on periodic trends in Sections 1.15-1.22 and 14.1-14.2. Because the nonmetals form molecular compounds, it would also be helpful to review Lewis structures, electronegativity, and covalent bonding in Chapters 2 and 3. The bulk properties of nonmetallic materials are affected by intermolecular forces (Sections 5.1-5.5). 

The oxides of main-group elements show periodic trends in properties. Oxides of metals tend to be ionic and to form basic solutions in water. Oxides of nonmetals are molecular and the anhydrides of acids. 

The group 4A elements exemplify the increase in metallic character down a group in the periodic table Carbon is a nonmetal silicon and germanium are semimetals and tin and lead are metals. The usual periodic trends in atomic size, ionization energy, and electronegativity are evident in the data of Table 19.4. 

The group 6A elements are oxygen, sulfur, selenium, tellurium, and polonium. As shown in Table 19.7, their properties exhibit the usual periodic trends. Both oxygen and sulfur are typical nonmetals. Selenium and tellurium are primarily non-metallic in character, though the most stable allotrope of selenium, gray selenium, is a lustrous semiconducting solid. Tellurium is also a semiconductor and is usually classified as a semimetal. Polonium, a radioactive element that occurs in trace amounts in uranium ores, is a silvery white metal. 

The semimetals, or metalloids, are known to exhibit some of the properties of metals and some of those of nonmetals. The semimetals are B, Si, Ge, As, Sb, Te, and At. They are highlighted in bold in the partial periodic table in Figure 4.1. The elements located to the left of the semimetals are the metals those to the right of the semimetals are the nonmetals. Identifying an element as a metal, nonmetal, or semimetal is important in identifying periodic trends and in identifying the types of bonds that atoms will form with each other. 

The immense number of chemical compounds formed by the halogens provides chemists with an extraordinary database from which numerous chemical and physical phenomena can be correlated with respect to various periodic trends. From databases like Inorganic Crystal Structure Data (ICSD, http //www.fiz-karlsruhe.de ) and International Centre for Diffraction Data (ICDD, http //www.icdd.com) with 67 000 and 25 000 entries, respectively, one can easily make out that halides are one of the dominant classes of compounds besides oxides. Even within the subset of inorganic solids, there is tremendous diversity of composition, stracture, and properties and to summarize this would create its own encyclopedia. Therefore, the discussion in this article is limited primarily to binary halides, their structures, and some of their properties, except halides of elements which are nonmetals. Binary actinide hahdes are discnssed elsewhere see Actinides Inorganic Coordination Chemistry). Complex hahdes (sohd phases containing two or more kinds of metal ions), ... 

Two factors determine how easily a proton is released from a nonmetal hydride the electronegativity of the central nonmetal (E) and the strength of the E—H bond. Figure 18.11 displays two periodic trends ... 

Understanding the wealth of information found in the organization of the periodic table is a central skill for general chemistry. You will always have a periodic table available for ACS exams, and likely for most classroom tests as well. Therefore, knowing the trends within the periodic table will allow prediction of properties, even for unfamiliar elements. Relative sizes of atoms and ions, trends in ionization energy, and trends in electronegativity are all important to understanding the behavior of elements. The differences between metals and nonmetals and their reactions are also based on periodic trends. Trends within families and trends within periods can both reveal much about the physical properties and chemical reactions expected for the elements. 

The periodic trends in the acid strengths of binary compounds of hydrogen and the nonmetals of periods 2 and 3 are summarized in FIGURE 16.17. 

Figure 2.14 Based on the periodic trend, we expect that elements that precede a nonreactive gas, as F does, will also be reactive nonmetals. The elements fitting this pattern are H and Cl.

TRENDS FOR SELECTED NONMETALS Finally, we examine some of the periodic trends in the chemistry of hydrogen and the elements in groups 6A, 7A, and 8A. 

Diagonal relationships are commonly observed between elements from the second and third series. This periodic trend is especially true for the following pairs of elements Li/Mg, Be/AI, and B/Si. While vertical periodic trends are still predominant, some properties match better along a diagonal. These diagonal periodic trends are no doubt related to the fact that the radius of an atom increases down and to the left in the periodic table, whereas I.E. and E.A increase up and to the right The diagonal nature of the metal-nonmetal line has already been discussed. 

We will examine some differences in the physical and chemical properties of metals and nonmetals. Finally, we discuss some periodic trends in the chemistry of the active metals (groups 1A and 2 A) and of several nonmetals (hydrogen and groups 6A to 8A). 

A Figure 7.12 The periodic table, showing metals, metalloids, nonmetals, and trends in metallic character. 

Figure 18.10 displays two periodic trends among the nonmetal hydrides ... 

Types of Bonding Three Ways Metals and Nonmetals Combine 277 Lewis Symbols and the Octet Rule 278 The Ionic Bonding Model 280 Why Ionic Compounds Form The Importance of Lattice Energy 280 Periodic Trends in Lattice Energy 281 How the Model Explains the Properties of Ionic Corrpounds 283... 

As noted earlier, metallic character increases in moving down a group of elements. Tin, which is between the metalloid germanium and the metal lead in Group IVA, illustrates this periodic trend in a very interesting way it has two different forms, or allotropes one is a metal and the other is a nonmetal. 

The alkaline-earth metals superimposed on the interconnected network of ideas. These include the trends in periodic properties, the acid-base character of metal and nonmetal oxides, trends in standard reduction potentials, (a) the uniqueness principle, (b) the diagonal effect, (c) the inert-pair effect, and (d) the metal-nonmetal line. 

Electron affinity is defined as the amount of energy required to remove an electron from a negative ion that is in the gaseous state. Since metals tend not to form negative ions, electron affinity really only applies to nonmetals. The trends for electron affinity are similar to the trend for ionization energy. As we move across a row of the periodic table from left to right, electron affinity generally increases. As we descend a column, electron affinity tend to decrease. 

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