1. Chapter 5 Section 2 Notes An ion is an atom or group of atoms that has an electric charge. When an atom loses an electron, it loses a negative charge and becomes a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion. Some ions are made of several atoms. Ions that are made of more than one atom are called polyatomic ions.

2. Positive ions and negative ions attract one another because they are oppositely charged. An ionic bond is the attraction between two oppositely charged ions. Ionic bonds form as a result of the attraction between two oppositely charged ions.

3. Ionic bonds form as a result of the attraction between positive and negative ions. A compound that consists of positive and negative ions is called an ionic compound. Compounds can be represented by chemical formulas.

4. A chemical formula is a combination of symbols that shows the ratio of elements in a compound. When ionic compounds form, the ions come together in a way that balances out the charges of the ions. The chemical formula for the compound reflects this balance.

5. An ionic compound is named according to certain rules. For ionic compounds, the name of the positive ion comes first, followed by the name of the negative ion. All ionic compounds are similar in some ways.

6. Ionic compounds are hard, brittle crystals that have high melting points. When dissolved in water or melted, they conduct electricity. The ions in ionic compounds form an orderly, three-dimensional arrangement called a crystal. Because ionic bonds are strong, a lot of energy is needed to break them. As a result, ionic compounds have high melting points and are solids at room temperature.