Aim: What properties do Ionic Compounds have? Do Now: What types of ions are in involved in ionic compounds? What types of elements are usually involved in forming ionic bonds? Explain, in terms of electrons, how ionic bonds are formed.

Ionic Bonding Process

Individual Practice Show the electron transfer between atoms of potassium and nitrogen. Determine how many atoms of each element are required. Draw the dot structure for the compound formed above. *3. What would be the chemical formula for the above compound?

Properties of Ionic Compounds Ionic substances form giant ionic crystals containing oppositely charged ions. High melting and boiling points - Ionic bonds are very strong - a lot of energy is needed to break them. So ionic compounds have high melting and boiling points Ionic Compounds are neutral Adding the charges of all the number of ions should equal zero

Properties continued Conductive when liquid - Ionic compounds can only conduct electricity if their ions are free to move. Ionic compounds do not conduct electricity when they are solid - only when dissolved in water or melted. A compound that conducts electricity is called an electrolyte.

Writing a chemical formula A chemical formula tells us the number of atoms of each element in a compound. It contains the symbols of the atoms of the elements present in the compound, as well as how many there are for each element in the form of subscripts.

Example: Aluminum Chloride Predicting Chemical Formula of Ionic Compounds Criss-Cross Rule Example: Aluminum Chloride Step 1: write out name with space Al Cl 3+ 1- Step 2: write symbols & charge of elements Al Cl Step 3: 1 3 criss-cross charges as subscripts Step 4: AlCl 3 combine as formula unit (“1” is never shown)

Example: Aluminum Chloride Criss-Cross Rule Example: Aluminum Chloride Step 1: Aluminum Chloride Step 2: Al3+ Cl1- Step 3: Al Cl 1 3 Step 4: AlCl 3

Example: Aluminum Oxide Criss-Cross Rule Example: Aluminum Oxide Step 1: Aluminum Oxide Step 2: Al3+ O2- Step 3: Al O 2 3 Step 4: Al2O3

Example: Magnesium Oxide Criss-Cross Rule Example: Magnesium Oxide Step 1: Magnesium Oxide Step 2: Mg2+ O2- Step 3: Mg O 2 2 Step 4: Mg2O2 Step 5: MgO

Practice Using Criss-Cross Method to Predict Ionic Formulas Predict the formulas of the ionic compounds formed form the following elements. Potassium and oxygen Magnesium and nitrogen K+1 O-2 K2O Mg+2 N-3 Mg3N2

Practice: Write the chemical formulas for the compound formed between the following atoms Barium and fluorine Barium and oxygen Aluminum and phosphorus Lead (II) and sulfur Lead (II) and chlorine **Roman Numeral indicates charge for transition metal**