Chapter 4 The Ionic Bond
4.8CHAPTER SUMMARY AND OBJECTIVES
The bonding electrons in ionic bonds reside totally on one of the atoms in the bond. This occurs when there is a large difference between the electronegativities of the bound atoms, which usually occurs when one atom is a
metal and the other a nonmetal. The electrons
added to the nonmetal give it a negative char
ge, while the reduced number of electrons on
the metal gives it a positive charge. The ioni
c bond results from the electrostatic attraction
of the opposite charges. Main group metals usually empty their valence shells to form cations with charges equal to their group nu
mbers. Most transition metals lose their
outermost s electrons to form +2 ions. Sn and Pb form only +2 ions, while Tl forms both +1 and +3 ions. The name of the cation is the same as that of the metal. Nonmetals fill their valence shell, so the charge on a nonmet
al anion equals its group number minus 8.
Anions are named by changing the end of the name of the nonmetal to -
ide
.
The oxidation state of an atom is the char
ge the atom would have if the bonds were
ionic. Oxidation states are used for electron counting in both ionic and non-ionic compounds. Some common elements have the same oxidation state in almost all of their compounds. Using that fact and a series of priorities, we can assign oxidation states to atoms in molecules or ions. The chemical form
ulas for binary molecules and ions can be
predicted by using the common oxidation states of the atoms and the fact that the oxidation states must sum to the charge on the species.
Polyatomic ions are ions that contain more
than one atom. Polyatomic ions are very
common, and most are oxoanions. The name of an
ionic substance is simply the name of
the cation followed by the name of the anion. Ionic compounds are solids at room temperature and exist as an extended network of ions, not as individual molecules.
After studying the material of this chapter, you should be able to: 1. describe what happens when a metal atom
reacts with a nonmetal atom (Section 4.1);- identify ionic compounds (Section 4.1); 3. determine the electron conf
igurations of monatomic anions and cations (Section 4.2);- predict the relative sizes of atoms and their ions (Section 4.3); 5. determine the oxidation stat
es of the atoms in an ion or molecule (Section 4.4);- use oxidation states to predict
formulas of compounds (Section 4.4);- write the formulas of common polyatomic ions (Section 4.5); 8. predict the formula of an oxoanion from its name (Section 4.6); 9. name ionic compounds (Section 4.6); and 10.
explain why ionic compounds are not molecular (Section 4.7).
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