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Drill What is the chemical formula when the following combine: Mg and O Al and Cl **Think criss-cross method!  Drill

Information Polyatomic Ions Criss-Cross Practice Reverse Criss-Cross Exit Slip Agenda

Determine the formula when given a polyatomic ion and another cation/anion Determine the charge on a metal when given a formula I Can…

Unit 3 Tests Grades are Updated on BCPSOne If you want to do a redo – best time is to do it right before break! Unit 3 Tests

Please Note If you were absent, best to take the test before break This information is going to be important to know as we continue in this class If you are confused, PLEASE see me ASAP to make sure you have an understanding!!!! Please Note

Charged molecules that contain two or more atoms covalently bonded. They are bounded very tightly together, so the ion retains its identity within an ionic compounds and over the course of many chemical reactions Polyatomic Ions

Hydroxide- OH- Why a Charge?

Do I have to Memorize them?? Yes and No You will be given a small list and then will have to determine the others Do I have to Memorize them??

Criss-Crossing with Polyatomic Ions Polyatomic ions DO NOT break apart when writing a chemical formula Criss-Crossing with Polyatomic Ions

Criss-Crossing with Polyatomic Ions If you have more than one polyatomic ion in the formula, you MUST put parentheses around it to show there are more than one of the polyatomic ions If there is only 1 atom, you DO NOT need to include parentheses around it Criss-Crossing with Polyatomic Ions

DO NOT DO Examples (Na)2(CO3) MgOH2 (NH4)(OH) Na2CO3 Mg(OH)2 NH4OH

Li and SO4-2 Al and CO3-2 NH4+ and PO4-3 Examples

Able to tell what charge metals have since some transition metals have different charges Example Reverse Criss Cross

Determining how many Atoms If you have parentheses, you must multiple the numbers together Determining how many Atoms

Exit Slip What is the chemical formula when Sr and OH combine? What is the chemical formula when NH4 and PO4 combine? What is the charge on the metal: Pb(CO2)2 How many oxygen atoms are in Al(NO3)3 Exit Slip