1. 15.2 Notes: Ionic Bonds

2. Learning Targets
Explain how the octet rule is related to bond formation
Identify the location of metals and nonmetals on the periodic table.
Describe how ionic bonds are formed
Discuss some important properties of ionic compounds

3. The Octet Rule
According to the octet rule, in forming compounds, atoms tend to combine with other atoms so that they each have 8 valence electrons

4. Formation of Ionic Bonds
Anions (negative ions) and cations (positive ions) have opposite charges.
They attract one another by electrostatic forces
The forces of attraction that bind these oppositely charged ions are called ionic bonds

5. Compounds that consist of groups of ions joined by electrostatic forces are called ionic compound
In any sample of an ionic compound, the total positive charges of the cations must equal the total negative charges of the anions

6. Consider the reaction between sodium and chlorine
Sodium has a single valence electron that it can easily lose
Chlorine has seven valence electrons and can easily gain one
When sodium and chlorine react to form a compound, the sodium atom gives up its valence electron and a chlorine ion accepts this electron

7. The chemical formula of sodium chloride (NaCl) represents a formula unit, or the lowest whole-number ratio of cations to anions in an ionic compound

8. An aluminum atom has 3 valence electrons while bromine has 7
Therefore, aluminum wants to lose its 3 electrons while bromine wants to gain one more electron
This means that when aluminum and bromine react, three bromine atoms combine with each aluminum atom (AlBr3)

9. Properties of Ionic Compounds
Ionic compounds are always composed of one nonmetal and one metal
Electrons transfer from a metal to a nonmetal
Where are metals located on the periodic table? What about nonmetals?
Metals = left of the stairs except hydrogen
Nonmetals = right of stairs and plus hydrogen
Elements never gain or lose more than 3 electrons as they form ionic compounds

11. When melted, ionic compounds can conduct electric current
At room temperature, most ionic compounds are solids because the forces between ions are very strong
Ionic solids have a high melting point
When melted, ionic compounds can conduct electric current
Ionic solids are also hard and dissolve easily in water

12. Review: What is electronegativity???
The ability of an atom to attract electrons to itself

13. Write the symbol and determine the charge for the following ions?
Calcium
Bromine
Aluminum
Magnesium
Nitrogen
Tellurium