Periodic property ionization energy

Periodic Properties, Ionization Potentials, and Energy of External Orbitals... 

We have developed a fairly complete picture of polyelectronic atoms that is quite successful in accounting for the periodic table of elements. We will next use the model to account for the observed trends in several important atomic properties ionization energy, electron affinity, and atomic size. 

The stability of the electronic configuration is indicated by the fact that each element has the highest ionization energy in its period, though the value decreases down the group as a result of increasing size of the atoms. For the heavier elements is it actually smaller than for first-row elements such as O and F with consequences for the chemical reactivities of the noble gases which will be considered in the next section. Nuclear properties, particularly for xenon, have been exploited for nmr spectroscopy and Mdssbauer... 

In this section we will consider how the periodic table can be used to correlate properties on an atomic scale. In particular, we will see how atomic radius, ionic radius, ionization energy, and electronegativity vary horizontally and vertically in the periodic table. 

Consider the fluorides of the second-row elements. There is a continuous change in ionic character of the bonds fluorine forms with the elements F, O, N, C, B, Be, and Li. The ionic character increases as the difference in ionization energies increases (see Table 16-11). This ionic character results in an electric dipole in each bond. The molecular dipole will be determined by the sum of the dipoles of all of the bonds, taking into account the geometry of the molecule. Since the properties of the molecule are strongly influenced by the molecular dipole, we shall investigate how it is determined by the molecular architecture and the ionic character of the individual bonds. For this study we shall begin at the left side of the periodic table. 

The usefulness of the main-group elements in materials is related to their properties, which can be predicted from periodic trends. For example, an s-block element has a low ionization energy, which means that its outermost electrons can easily be lost. An s-block element is therefore likely to be a reactive metal with all the characteristics that the name metal implies (Table 1.4, Fig. 1.60). Because ionization energies are... 

Elements on the left of the p block, especially the heavier elements, have ionization energies that are low enough for these elements to have some of the metallic properties of the members of the s block. However, the ionization energies of the p-block metals are quite high, and they are less reactive than those in the s block. The elements aluminum, tin, and lead, which are important construction materials, all lie in this region of the periodic table (Fig. 1.61). 

A. The phenomenon of periodicity is particularly clear in the melting points of the elements. It is however remarkable, because this is a purely physical property. The melting point is not an atomic property, but is determined by the relationships in the crystal lattice. Therefore the maxima and minima do not coincide with the beginning or end of a period as is the case with the atomic radii and ionization energies. 

The goal of this chapter is to help you relate the properties of elements to their position on the periodic table. These properties include ionization energies and electron affinities. You may want to review the basic structure of the periodic table in Chapter 2 and electron configurations in Chapter 7. And Don t forget — Practice, Practice, Practice. 

Periodic trends in ionization energy are linked to trends involving the reactivity of metals. In general, the chemical reactivity of metals increases down a group and decreases across a period. These trends, as well as a further trend from metallic to non-metallic properties across a period, and increasing metallic properties down a group, are shown in Table 3.1. 

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