Electronic Arrangements in Atoms

In this chapter, we focus on electron arrangements in atoms, paying particular attention to the relative energies of different electrons (energy levels) and their spatial locations (orbitals). Specifically, we consider the nature of the energy levels and orbitals available to—... 

The periodicity of chemical properties, which Is summarized In the periodic table. Is one of the most useful organizing principles in chemistry. Periodic patterns also provide information about electron arrangements in atoms. 

One of the most striking things about the chemistry of the elements is the periodic repetition of properties. There are several groups of elements that show great similarities in chemical behavior. As we saw in Chapter 2, these similarities led to the development of the periodic table of the elements. In this chapter we will see that the modern theory of atomic structure accounts for periodicity in terms of the electron arrangements in atoms. 

Two big questions remained about electrons in atoms (1) How are electrons arranged in atoms (2) How do these electrons behave We now have the background to consider how modern atomic theory answers these questions. 

We will now describe the electron arrangements in atoms with Z = 1 to Z = 18 by placing electrons in the various orbitals in the principal energy levels, starting with n = 1, and then continuing with n = 2, n = 3, and so on. For the first 18 elements, the individual sublevels fill in the following order Is, then 2s, then 2p, then 3s, and then 3p. 

Niels Bohr publishes a theory of atomic structure relating the electron arrangement in atoms and atomic chemical properties. 

The first ideas about electronic arrangement in atoms were primarily figured out from atomic emission spectra. In various experiments, atoms were made to be thermally or electrically excited, and this resulted in different kinds of bands or lines on photographic plates. Our understanding of atomic structure is based on these types of experiments. All elements have their characteristic line spectra with which they can be analyzed and identified. 

In this chapter we will look at atomic structure in more detail. In particular, we will develop a picture of the electron arrangements in atoms—a picture that allows us to account for the chemistry of the various elements. Recall from our discussion of the periodic table in Chapter 4 that, although atoms exhibit a great variety of characteristics, certain elements can be grouped together because they behave similarly. For example, fluorine, chlorine, bromine, and iodine (the halogens) show great chemical similarities. 

You can draw an analogy here with the stability of closed shell electronic arrangements in atoms. 

Good introduction to electron arrangements in atoms with examples. 

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