The Representative Elements

Representative elements Atomic Size and Group Anomalies 

4 The Group 2A Elements The Group 3A Elements The Group 4A Elements The Group 5A Elements The Chemistry of Nitrogen 

Nitrogen Hydrides Nitrogen Oxides Oxyacids of Nitrogen 20.9 The Chemistry of Phosphorus Phosphorus Oxides and Oxyacids 

Phosphorus in Fertilizers 20.10 The Group 6A Elements The Chemistry of Oxygen The Chemistry of Sulfur Sulfur Oxides Oxyacids of Sulfur 

0 far in this book we have covered the major principles and explored the most important models of chemistry. In particular, we have seen that the chemical properties of the elements can be explained very successfully by the quantum mechanical model of the atom. In fact, the most convincing evidence of that model s validity is its ability to relate the observed periodic properties of the elements to the number of valence electrons in their atoms. 

1 A Survey of the Representative 20.6 The Group 4A Elements 20.10 The Group 6A Elements 

2 The Group lA Elements Nitrogen Oxides Oxyacids of Sulfur 

3 The Chemistry of Eiydrogen Oxyacids of Nitrogen 20.13 The Group 7A Elements 

5 The Group 3A Elements Phosphorus Oxides and Oxyacids Oxyacids and Oxyanions 

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Figure 19 The representative element used with Cox analysis. The miner cylinder represents the fiber and outer as the matrix.

This statement applies to the representative elements. Multiple bonding is also important for some transition elements. For a review of metal-metal multiple bonds, see Cotton, F.A. J. Chem. Educ., 1983, 60, 713. 

Lewis dot representations for the representative elements show only the valence electrons in the outermost occupied s and p orbitals. Paired and unpaired electrons are also indicated. 

The representative elements have valence electrons in. v or. v and p orbitals in the outermost occupied energy level, whereas the /-transition metals must have a partially filled set of d orbitals. 

The electrons that are contained in the noble gas core are the core electrons while the electrons outside the core are valence electrons. These valence electrons are involved in the chemical behavior of the elements. For the representative elements, the valence electrons are those s and p electrons in the outermost energy level. The valence shell contains the valence electrons. 

The octet rule doesn t always work, but for the representative elements, it works a majority of the time. 

For the representative elements, the valence electrons are all electrons in the outer s and p orbitals of an atom. A quick way of determining the number of valence electrons is to locate the element on the periodic table. There are eight columns of representative elements. The first column, headed by H and Li, has one valence electron, the second column has two, skip the transition elements, the next column, headed by B and Al, has three. This continues to the last (eighth) column where there are eight valence electrons. The only exception to this procedure is helium, which only has two valence electrons. 

As a first approximation, the valences of the representative elements can be predicted from their position on the periodic table. Hydrogen and the metals have positive charges... 

What do elements look like How do they behave Can periodic trends in the properties of elements be observed You cannot examine all of the elements on the periodic table because of limited availability, cost, and safety concerns. However, you can observe several of the representative elements, classify them, and compare their properties. The observation of the properties of elements is called descriptive chemistry. 

Making a Model Construct a periodic table and label the representative elements by group (1A through 7A). Using the information in your data table and the periodic table, record the identities of elements observed during the lab in your periodic table. 

Elements that appear in the s block and the p block are called either the main group elements or the representative elements. Chemists give them these names because, collectively, these elements are representative of a wide range of physical and chemical properties. Among the main group elements, for example, you will find metals, non-metals, metalloids. 

Most inorganic research involves work with small molecules, and relatively little concentrated effort has been devoted to the macromolecular aspects of the subject. The complexity of the macromolecular chemistry has undoubtedly contributed to this neglect. However, it is clear from recent work that dramatic advances in both fundamental science and technology would be possible if the high polymer chemistry of the representative elements were to be studied in detail. Indeed, the much-heralded renaissance in Main Group chemistry may ultimately depend on a closer Investigation of the macromolecular aspects of the field. 

A summary is given of the structures for the known homopolyatomlc anions of the representative elements from groups IV and V and for a variety of heteropolyatomlc examples. Also considered are factors Important In their stabilization, electronic requirements, Isoelectronlc analogs, and new results for Sby3, Sb 2- Pb2Sb2 and the unusual i[KSng ]. The contributions of Ralph Rudolph to the study of these anions In solution are noted. 

How do you predict the charge of the ions derived from the representative elements ... 

Do you see the pattern For the representative elements, the number of valence electrons is equal to the group number. This is why the authors believe the older AB numbering system for the periodic table is superior to the serial (1-18) numbering system. For the A-group elements, the number of valence electrons is equal to the group number. The B-group elements, or transition elements, are not as easy, and we will skip them for the purposes of our discussion. 

Figure 4.11 Atomic radii for the first five periods of the representative elements. All units are in angstroms (A).

The elements in the eight A groups are the main-group elements. They are also called the representative elements. 

The basic features of the periodic table are summarized here. Most of your work in this course will focus on the representative elements. 

The periodic table. The elements in the A groups are the representative elements. The elements shown in pink are called transition metals. The dark line approximately separates the nonmetals from the metals. The elements that have both metallic and nonmetallic properties (semimetals) are shaded in blue. 

The traditional form of the periodic table is shown in Fig. 18.1. Recall that the representative elements, whose chemical properties are determined by the valence-level s and p electrons, are designated Groups 1A through 8A. The transition metals, in the center of the table, result from the filling of d orbitals. The elements that correspond to the filling of the 4/ and 5f orbitals are listed separately as the lanthanides and actinides, respectively. 

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