Chapter 20: Metals and Their Compounds

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In this and the next lecture, we see how we can predict some of the bulk properties of matter using simple patterns in the Periodic Table. The patterns of the Periodic Table are not perfect and sometimes there are exceptions, but in this course we will focus on the patterns and not on the exceptions. Pattern: The elements of the Periodic Table can be divided into (metals, nonmetals?) on the left-hand-side and to the upper right. This division of the elements creates three cases of interest: the bond between atoms that are both metals, the bond between an atom that is a metal and an atom that is a non-metal, and the bond between two nonmetal atoms. Characteristics of the Metallic Bond: Usually (solid, liquid, gas?) at room temperature; Readily conducts ; Shiny (smooth) or white (rough). Color may appear as an exception; Malleable; Conducts ; Chemically active (readily forms compounds). act as a glue to hold metal atoms together to form a piece of metal. If the valence electrons form orbitals that encompass many metal atoms, spreading essentially thoughout the piece of metal, and if the electrons in these orbitals have less energy than they would have in individual atoms, the negative electron orbitals form a glue to hold the positive nuclei together. Under these circumstances, the (Uncertainty, Exclusion?) Principle requires that there are very many electron energy levels in the metal that are very close together. The metallic bond explains in a very simple conceptual way why metals form allows and why metals are shiny and opaque. For example, metals are opaque because there are many, many energy levels close together (Exclusion Principle says they can't all be in identical orbitals) and hence a photon of almost any energy can be absorbed by giving its energy to an electron and causing the electron to jump to a higher energy level. The photon is therefore "stopped"; the metal is opaque. Pattern: The electrons in the atoms of the Noble Gas family have particularly low average energy. There is a tendency for atoms in columns near the Noble Gases to "want to be like the nearest Noble Gas" in order to lower the energy of their electrons. Metal atoms can become like a Noble Gas by giving away their electrons. Nonmetal atoms can become like Noble Gas atoms by accepting extra electrons to fill their shell. When a metal and a nonmetal atoms interact, the metal atom may give its valence electrons to the nonmetal atom so that the average energy of all of their electrons is as low as possible. This arrangement is called a(n) (covalent, ionic, metallic?) bond. The orbital of the transferred valence electron is actually localized around the (positive, negative?) ion. The positive ion has lost an electron in the sense that the orbital ("probability") of the valence electron is no longer centered on the positive ion, but rather has moved to center on the negative ion. Definition: The "oxidation state" of an atom in an ionic bond is the number of valence electrons the metal atoms has given up in the bond (with a (plus, minus?) sign) or the number of electrons the nonmetal atom has gained in the bond (with a (plus, minus?) sign.) In the ionic compound, sodium chloride (NaCl), sodium has an oxidation state of (+1, -1?) and chlorine has an oxidation state of . Since a single sodium atom gives away one electron and a single chlorine atom accepts one electron, there will be one sodium and one chlorine atom in the compound, i.e., NaCl. The balanced equation for the formation of NaCl is, Na + Cl2 ---> NaCl. Characteristics of the Ionic Bond: White, crystalline solid (color is an occasional exception); (Brittle, malleable?) ; (Does, does not?) readily conduct heat; (Does, does not?) readily conduct electricity in solid form; (Does, does not?) conduct electricity when dissolved or melted; (Transparent, opaque?) as a crystal.

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