Aim: What are polyatomic ions Aim: What are polyatomic ions? DO NOW: Answer the following questions on a separate sheet of paper. Given the structural formula: The bond between which two atoms has the greatest degree in polarity? C and C C and O H and C H and O 2. Which molecule has a polar covalent bonds? H-H O=C=O .

Refresh! Write the formula for the compound magnesium chloride 2. Write the name for Fe2O3

NH4+ Think. Pair. Share. What type of elements are in the formula? What type of bonds do you think are between the atoms in this formula? The formula also has a charge. What type of bond do you think these group of atoms might form? Why?

Polyatomic Ions (Table E) A polyatomic ion is a tightly bound group of atoms that has a positive or negative charge and behave as a unit. A group of atoms that are covalently bound and as a whole have a charge. Ex: The carbonate ion (CO32-) consists of one carbon atom and three oxygen atoms and carries an overall charge of 2−. 

**The vast majority of polyatomic ions are anions, many of which end in –ate or –ite.

New definition of Ionic Bond Chemical bond between positive and negative ions Metal ion and nonmetal ion Polyatomic ion and nonmetal ion Metal ion and polyatomic ion Polyatomic ion and polyatomic ion

1. Which compound contains both ionic and covalent bonds? HBr CBr4 NaBr NaOH

2. Which polyatomic ion contains the greatest number of oxygen atoms? Acetate Carbonate Hydroxide peroxide

3. Which formula represents a hydronium ion? H3O+ NH4+ OH- HCO3-

4. What is the name of the polyatomic ion in the compound Na2O2? Hydroxide Oxalate Oxide peroxide

Naming ionic compounds with polyatomic ions Steps for naming: 1. Name the metal with its full name. 2. Identify the polyatomic ion at the end of the formula, use its name. naming examples: Ca(NO3)2 Ca ( NO3 ) 2 calcium nitrate KNO3 K NO3 potassium nitrate Ba(OH)2 Ba ( OH ) 2 barium hydroxide Li2CO3 Li 2 CO3 lithium carbonate Al2(SO4)3 Al 2 ( SO4 ) 3 aluminum sulfate NH4ClO3 NH4 ClO3 ammonium chlorate

Writing formulas for compounds with polyatomic ions from the names Balancing charges Method Criss Cross Method Ex: Sodium carbonate 1. Identify ions Na+1 CO3-2 2. Balance out charges using multpipliers (+1) = (-2) 3. Write formula Na2CO3 Ex: Sodium Carbonate 1. Identify ions Na+1 CO3-2 2. Cross over superscripts (charges) 3. Write out formula. Simplify if necessary Na2(CO3)1 Na2CO3 2 1

Summary Write in your notebooks why a compound that includes a polyatomic ion has both ionic and covalent bonding.

Determining the Number of Atoms of Each Element in a Compound Given the following formula: Mg (NO3)2, determine the number of atoms for magnesium, nitrogen and oxygen Mg = 1 N = 1 x 2 = 2 O= 3 x 2 = 6 You try! Determine the number of atoms of each element for Ca3(PO4)2

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