“Perhaps one of you gentlemen would mind telling me just what is outside the window that you find so attractive..?” Image courtesy NearingZero.net

Example: Aluminum Chloride Criss-Cross Rule Example: Aluminum Chloride 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 subsrcipts 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

Naming Binary Compounds Formula Name barium oxide BaO ____________________ ________________ sodium bromide MgI2 ____________________ KCl ____________________ ________________ strontium fluoride ________________ cesium fluoride NaBr magnesium iodide potassium chloride SrF2 CsF

Rules for Parentheses Parentheses are used only when the following two condition are met: There is a radical (polyatomic ion) present and… There are two or more of that radical in the formula. Examples: NaNO3 NO31- is a radical, but there is only one of it. Co(NO3)2 NO31- is a radical and there are two of them (NH4)2SO4 NH41+ is a radical and there are two of them; SO42- is a radical but there is only one of it. Co(OH)2 OH1- is a radical and there are two of it. Al2(CO3)3 CO32- is a radical and there are three of them. NaOH OH1- is a radical but there is only one of it.