Starter #28Starter #28What is the symbol and name for the What is the symbol and name for the

compound formed from mixing compound formed from mixing Cobalt (+2) and chlorineCobalt (+2) and chlorine

POLYATOMIC COMPOUNDS POLYATOMIC COMPOUNDS (Challenge)(Challenge)

Chapter 5.9Chapter 5.9

Polyatomic CompoundsPolyatomic CompoundsAre groups of atoms that tend to Are groups of atoms that tend to

stay together and carry an stay together and carry an overall ionic charge.overall ionic charge.

Example: Example: Nitrate ionNitrate ion

When a compound containing this ion is When a compound containing this ion is dissolved in water, the positive metal ion dissolved in water, the positive metal ion and the nitrate ion separate from each and the nitrate ion separate from each other, but the nitrate ion itself stays other, but the nitrate ion itself stays together as a unit surrounded by water together as a unit surrounded by water molecules.molecules.

Some ionic compounds are made of Some ionic compounds are made of polyatomic ions which is an ion with polyatomic ions which is an ion with more than one element in it.more than one element in it.

Looking at the top center of your Periodic Looking at the top center of your Periodic Chart of Ions handout you will see Chart of Ions handout you will see examples of theseexamples of these

Examples:Examples: COCO33

2-2- Carbon CarbonateateNONO33

1-1- Nitr Nitrateate

NoteNote: you will know the difference : you will know the difference between a regular non-metal ion and a between a regular non-metal ion and a polyatomic ion by the fact that there is polyatomic ion by the fact that there is no no “ide”“ide” ending on the polyatomic ion. ending on the polyatomic ion.

WRITING FORMULAS FOR WRITING FORMULAS FOR POLYATOMIC COMPOUNDSPOLYATOMIC COMPOUNDS

All the compound formula calculations All the compound formula calculations and compound naming procedures are and compound naming procedures are the same as for regular ionic the same as for regular ionic compounds.compounds.

EXAMPLE:EXAMPLE:What is the formula for the ionic What is the formula for the ionic

compound formed by sodium and compound formed by sodium and sulfate ion?sulfate ion?

STEPSSTEPS1) Write the symbols of the metal and of the 1) Write the symbols of the metal and of the

polyatomic grouppolyatomic groupNa SONa SO44

2) Write the ionic charges2) Write the ionic chargesNaNa+1+1 SO SO44

-2-2

3) Choose the number of ions to balance the 3) Choose the number of ions to balance the chargecharge

NaNa+1+1 Na Na+1+1 SO SO44-2-2

STEPSSTEPS

4) Write the formula using subscripts.4) Write the formula using subscripts.

NaNa22SOSO44

You could use the criss-cross rule if You could use the criss-cross rule if you wanted to.you wanted to.

EXAMPLE 2EXAMPLE 2What is the formula for lead (IV) What is the formula for lead (IV)

carbonate?carbonate?

1) Pb CO1) Pb CO33

2) Pb2) Pb+4+4 CO CO33-2-2

3) criss-cross rule3) criss-cross rule4) Pb4) Pb22(CO(CO33))44

(must reduce)(must reduce)5) Pb(CO5) Pb(CO33))22

Starter #29Starter #29What is the name and formula for the What is the name and formula for the

compound formed by calcium and compound formed by calcium and nitrate?nitrate?

Try ThisTry ThisPAGE 198; 3 abce, 4 abdPAGE 198; 3 abce, 4 abd

QuestionsQuestions3. Write the formula for:3. Write the formula for:a) sodium phosphatea) sodium phosphateb) calcium sulfate b) calcium sulfate c) potassium chlorate c) potassium chlorate e) beryllium nitratee) beryllium nitrate

4. Name the following compounds:4. Name the following compounds:a) Ka) K22C0C033b) Nab) Na22SOSO44d) AgNOd) AgNO33

SOLUTIONSSOLUTIONS3a) Na3a) Na33POPO44

3b) CaSO3b) CaSO44

3c) KClO3c) KClO33

3e) Be(N03e) Be(N033))22

4a) Potassium Carbonate4a) Potassium Carbonate4b) Sodium Sulfate4b) Sodium Sulfate4d) Silver Nitrate4d) Silver Nitrate