Chemical properties valence electron configurations

A primary goal of the periodic table is to assist recognition of the ground-state valence electron configuration of each atom, the chief determinant of its chemical properties" ([21], p 5). 

All the elements in a main group have in common a characteristic valence electron configuration. The electron configuration controls the valence of the element (the number of bonds that it can form) and affects its chemical and physical properties. Five atomic properties are principally responsible for the characteristic properties of each element atomic radius, ionization energy, electron affinity, electronegativity, and polarizability. All five properties are related to trends in the effective nuclear charge experienced by the valence electrons and their distance from the nucleus. 

As in the discussion of hydrogen, in this section we examine the properties of the alkali metals in the context of the periodic table and focus on significant applications of the elements and selected compounds. The valence electron configuration of the alkali metals is s1, where n is the period number. Their physical and chemical properties are dominated by the ease with which the single valence electron can be removed (Table 14.3). 

Ion formation is only one pattern of chemical behavior. Many other chemical trends can be traced ultimately to valence electron configurations, but we need the description of chemical bonding that appears in Chapters 9 and 10 to explain such periodic properties. Nevertheless, we can relate important patterns in chemical behavior to the ability of some elements to form ions. One example is the subdivision of the periodic table into metals, nonmetals, and metalloids, first introduced in Chapter 1. 

Periodic table A chart that arranges the elements by atomic number in a way that the vertical columns produce groups of elements with similar valence electron configurations and chemical properties. 

The valence electron configuration explains why groups define chemical families that exhibit similar chemical properties. Because it is the valence electrons that determine an element s chemical behavior, and groups have similar valence electron configurations, then elements in the same group display similar chemical behavior. The electron configuration also explains the... 

The valence electron configurations of the elements in the same group are the same. Therefore, elements in the same group show similar chemical behaviors in a chemical reaction, but their physical properties may gradually change. 

Note in Fig. 12.26 that a very important pattern is developing The elements in the same group (vertical column of the periodic table) have the same valence electron configuration. Remember that Mendeleev originally placed the elements in groups based on similarities in chemical properties. Now we understand the reason behind these groupings. Elements with the same valence electron configuration often show similar chemical behavior. 

The essence of the periodic table is that members of each group of representative elements exhibit similar chemical properties that change in a regular way. The quantum mechanical model has allowed us to understand that the similarity of properties of the atoms in a group arises from the identical valence electron configurations shared by group members. It is the number and type of valence electrons that primarily determine an atom s chemistry. 

Elements in the same group on the periodic table have similar chemical properties because they have the same valence electron configuration. 

Because we have learned to associate similar chemical properties with similar valence-electron arrangements, we predict that the valence-electron configuration for potassium is 4s, resembling sodium (3s ) and lithium (2s ). That is, we expect the last electron in potassium to occupy the 4s orbital instead of one of the 3d orbitals. This means that the principal energy level 4 begins to fill before level 3 has been completed. This conclusion is confirmed by many types of experiments. So the electron configuration of potassium is... 

Elements in the same group of the periodic table possess the same number of electrons in their outer shells and are therefore said to have the same valence electronic configuration, and consequently similar chemical and physical properties. As electrons are filled into the inner shells of an atom, the outer shell takes on a specific valence configuration that is determined by the rules that govern how many electrons can occupy a particular shell, as described above in the section on quantum mechanics. It is this very regularity in the number of outer-shell electrons that explains the periodic behavior shown by the elements as the atomic number increases. Similarly, properties such as atomic size are determined by the number of shells an atom contains. For example, the radius of the atoms of the elements within a particular group in the periodic table increases from the top of the group to the bottom. 

The heavy black line in Fig. 20.1 separates the metals from the nonmetals, except for one case. Flydrogen, which appears on the metal side, is a nonmetal. Some elementsjust on either side of this line, such as silicon and germanium, exhibit both metallic and non-metallic properties. These elements are often called metalloids, or semimetals. The fundamental chemical difference between metals and nonmetals is that metals tend to lose their valence electrons to form cations, which usually have the valence electron configuration of the noble gas from the preceding period. On the other hand, nonmetals tend to gain electrons to form anions that exhibit the electron configuration of the noble gas in... 

Chemical properties are determined by their s and p valence-electron configurations... 

The periodic table, described in Section 1.1, was an empirical construction. However, it is fundamentally understandable in terms of the electron configurations just discussed. The chemical and many physical properties of the elements are simply controlled by the valence electrons. The valence electron configuration varies in a systematic and repetitive way as the various shells are filled. This leads naturally to both the periodicity and the repetitive features displayed in the periodic table (Figure 1.9). 

Describe how valence electron configurations account for some of the similarities in chemical properties among elements in a group. 

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