tightly bonded group of atoms with a + or – charge overall Section 4: Polyatomic Ions O H N H N O O H H polyatomic ion: tightly bonded group of atoms with a + or – charge overall O O O P S O O O O O

Common Polyatomic Ions Name Formula Charge ammonium NH4+ +1 hydroxide OH– -1 acetate C2H3O2– nitrate NO3– nitrite NO2– bicarbonate HCO3– carbonate CO32– -2 sulfate SO42– sulfite SO32– phosphate PO43– -3 handout list of polyatomics

Names and Formulas for Compounds with Polyatomic Ions Same rules as with all compounds. Example: calcium nitrate symbols of ions with charges (as superscripts) crisscross (to get subscripts) erase charges use ( ) for multiple polyatomic ions Ca2+ NO3– Ca2+ NO3– CaNO32 ? Ca(NO3)2

(use your polyatomic ions sheet) Write the formulas for the following compounds with polyatomic ions. (use your polyatomic ions sheet) ammonium nitrate calcium phosphate iron(III) carbonate NH4+ NO3– NH4NO3 Ca2+ PO43– Ca3(PO4)2 Fe3+ CO32– Fe2(CO3)3

1. Which of the following are positively charged polyatomic ions? Quick Quiz! 1. Which of the following are positively charged polyatomic ions? 1) ammonium ion 2) nitrate ion 3) iron(III) ion 1 only 2 only 1 and 2 1 and 3 NH4+ NO3– Fe3+

2. What is the correct name for Mg(OH)2 ? magnesium oxide Quick Quiz. 2. What is the correct name for Mg(OH)2 ? magnesium oxide magnesium hydroxide magnesium(II) hydroxide magnesium(II) hydroxate

Cu+ SO42– 3. What is the correct formula for copper(I) sulfate? CuS Quick Quiz. 3. What is the correct formula for copper(I) sulfate? CuS CuSO4 Cu2SO4 Cu(SO4)2 Cu+ SO42–

4. Which one of the following formulas is named correctly? Quick Quiz. 4. Which one of the following formulas is named correctly? sodium bicarbonate, Na2CO3 potassium nitrate, KNO2 sodium acetate, NaC2H3O2 lithium sulfide, Li2SO4