6.1 Ionic Bonding
Reading Focus
Key Concepts
When is an atom unlikely to react?- What is one way in which elements can achieve stable electron configurations?
- How does the structure of an ionic compound affect its properties?
Vocabulary
electron dot diagram
ion
anion
cation
chemical bond
ionic bond
chemical formula
crystals
Reading Strategy
Sequencing Copy the concept map. As you read, complete the concept map to show what happens to atoms during ionic bonding.
Figure 1 The handle and body of this titanium mug were welded together in an argon atmosphere. If titanium is allowed to react with oxygen in air, the compound that forms makes the weld more brittle and more likely to break.
The handle of the titanium mug in Figure 1 was joined to the body by welding. The pieces were heated until their surfaces fused together. The welding of titanium does not take place in air. At the temperature at which welding occurs, titanium becomes hot enough to react with oxygen in the air, forming an oxide. The oxide makes the weld more brittle and likely to break. Because titanium does not react with a noble gas such as argon, the welding of titanium usually takes place in an argon atmosphere.
Argon's name is a reminder of its inactivity. It comes from the Greek word argos, which means “idle” or “inert.” Why is argon very inactive yet oxygen is highly reactive? Chemical properties, such as reactivity, depend on an element's electron configuration.
Stable Electron Configurations
The highest occupied energy level of a noble gas atom is filled. When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react. The noble gases have stable electron configurations with eight valence electrons (or two in the case of helium).
The chemical properties of an element depend on the number of valence electrons. Therefore, it is useful to have a model of atoms that focuses only on valence electrons. The models in Figure 2 are electron dot diagrams. An electron dot diagram is a model of an atom in which each dot represents a valence electron. The symbol in the center represents the nucleus and all the other electrons in the atom.
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