Compound Review Elements naturally exist in compounds 2 or more chemically combined elements They form compounds to be more stable = have full outer energy levels of electrons 8 for every element but H and He Two main types of bonds are ionic and covalent Ionic = between a metal and nonmetal. The metal transfers electrons to the nonmetal. Covalent = between nonmetals. Electrons are shared.

Ionic Compounds An ionic compound is made of charged ions Cation = positively charged metal ion Positive because metals lose electrons Anion = negatively charged nonmetal ion Negative because nonmetals gain electrons Although an ionic compound is made up of charged ions, the overall charge of the compound must be zero Aka– the amount of (+) charge must equal the amount of (-) charge

How to determine the Chemical Formula for an Ionic Compound Name  Formula Write down the ions of each element with charge. (aka the symbol with its oxidation #) Determine the # of each ion it takes to make a compound with no charge. (aka “crisscross applesauce” the charges) Write down the formula using subscripts to show how many of each ion it took. Reduce/simplify. (if needed)

Example: What is the formula for the compound that forms between magnesium and phosphorous? Mg+2 P-3 Mg3P2 3(+2) + 2(-3) = 0

Practice Time! Write the chemical formulas if the elements below formed compounds. Aluminum and Chlorine Lithium and Nitrogen Magnesium and Iodine Calcium and Oxygen Sodium and Sulfur AlCl3 Li3N MgI2 CaO Na2S

How to Name Ionic Compounds Formula  Name Write the name of the first element. (the metal) Write the name of the second element (the nonmetal) with an –ide ending. Example: CaS Calcium sulfide

Practice Time! Write the name of the compounds based on the chemical formulas below. Be3N2 Na2O K3P AlN MgCl2 Beryllium Nitride Sodium Oxide Potassium Phosphide Aluminum Nitride Magnesium Chloride

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Exception #1: Polyatomic Ions Polyatomic Ions = a positively or negatively charged, covalently bonded, group of atoms Common ones to know: Ammonium - NH4+1 Sulfate - SO4-2 Nitrate - NO3-1 Carbonate - CO3-2 Hydroxide - OH-1 Acetate - C2H3O2-1 Phosphate - PO4-3 Chlorate - ClO3-1

How to Name Ionic Compounds Formula  Name Write the name of the first element (the metal) Exception #1: if polyatomic ion, use special name Write the name of the second element (the nonmetal) with an –ide ending Exception #1: if polyatomic ion, use special name. No –ide ending. Examples: Na3PO4 MgSO4 NH4Cl Sodium phosphate Magnesium sulfate Ammonium chloride

Practice Time! With Exception #1 Write the name of the compounds based on the chemical formulas below. NaNO3 CaSO4 (NH4)2O Mg3(PO4)2 NH4NO3 Sodium Nitrate Calcium Sulfate Ammonium Oxide Magnesium Phosphate Ammonium Nitrate

How to determine the Formula for an Ionic Compound w/ polyatomic ions Name  Formula Write down the ions of each element with charge (aka the symbol with its oxidation #) (just keep polyatomic ion in parentheses) Determine the # of each ion it takes to make a compound with no charge (aka “crisscross applesauce” the charges) (keep subscripts outside of parentheses and don’t change ANYTHING inside) Write down the formula using subscripts to show how many of each ion it took Reduce/simplify (if needed) Calcium phosphate Ca+2 (PO4) -3 Ca3(PO4)2

Practice Time! With Exception #1 Determine the chemical formulas for the following chemical compounds. Barium sulfate Aluminum carbonate Calcium nitrate Sodium acetate Potassium phosphate BaSO4 Al2(CO3)3 Ca(NO3)2 NaC2H3O2 K3PO4

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Transition Metals copper (I)  copper (II)  Cu+1 Cu+2 Transition metals “transition” because they can form many different ions Ex. Sodium is always Na+1 because it is in group 1 and group 1 metals have one valence electron  therefore they lose 1 e- to be stable Iron as a transition metal can be Fe+2 or Fe+3 Because you can’t determine the oxidation number from the periodic table, a Roman Numeral is used to show it copper (I)  copper (II)  Cu+1 Cu+2

Exception #2: Transition Metals How to Name Ionic Compounds (formula  name) Write the name of the first element (the metal) Exception #2: if a transition metal, include a Roman numeral to indicate the charge of the metal Write the name of the second element (the nonmetal) with an –ide ending Examples: CuCl CuCl2 Copper (I) Chloride Copper (II) Chloride

Determining the Roman Numeral for Transition Metals Option 1: Reverse crisscross Option 2: Use visuals or math to determine what charge of cation must be for overall charge to be zero.  Regardless of option you prefer, ALWAYS double check!! Ex. #1: Sn3(PO4)4 Option 2: Option 1: -3 Sn? (PO4)-3 ? Sn3(PO4)4 -3 ? Tin (IV) phosphate ? -3 Tin (IV) phosphate 3(?) = +12 -3 +4 4(-3) = -12

Determining the Roman Numeral for Transition Metals Option 1: Reverse crisscross Option 2: Use visuals or math to determine what charge of cation must be for overall charge to be zero.  Regardless of option you prefer, ALWAYS double check!! Ex. #2: FeSO4 Option 2: Option 1: ? -2 Fe? (SO4)-2 FeSO4 1(?) = +2 1(-2) = -2 Since the 2 isn’t there, it must have reduced. These are harder! What would it be then? +2 Iron (II) sulfate Iron (II) sulfate

Practice Time! With Exception #2 Write the name of the compounds based on the chemical formulas below. FeCl3 CrO Mn2O7 CrN Ag2S Iron (III) Chloride Chromium (II) Oxide Manganese (VII) Oxide Chromium (III) Nitride Silver (I) Sulfide

How to determine the Formula for an Ionic Compound w/ transition metals (name  formula) Write down the ions of each element with charge (aka the symbol with its oxidation #) (The transition metals charge will be given by the use of Roman Numerals.) Iron (II) Oxide Determine the # of each ion it takes to make a compound with no charge (aka “crisscross applesauce”) Write down the formula using subscripts to show how many of each ion it took Fe2O2 Reduce/simplify (if needed) FeO Fe+2 O-2

Practice Time! With Exception #2 Determine the chemical formulas for the compounds below based on the names. Copper (II) sulfide Iron (I) nitride Manganese (IV) oxide Chromium (VI) sulfide Titanium (IV) bromide CuS Fe3N MnO2 CrS3 TiBr4

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SUMMARY: Steps for Naming Ionic Compounds (formula  name) Name the metal (cation) Exception #1 = If polyatomic ion, use its special name Exception #2 = If a transition metal, use a Roman Numeral to indicate the charge of the metal Name the nonmetal (anion) with –ide ending Exception #1 = If polyatomic ion, use its special name, no -ide

Practice Time! Formula  Name MgCl2 (NH4)3PO4 Ni(OH)2 Magnesium chloride Ammonium phosphate Nickel (II) hydroxide

SUMMARY: Steps for Writing Chemical Formulas for Ionic Compounds (name  formula) Write down the ions with charge Crisscross the charges to determine subscripts (aka “criss cross applesauce”) (keep subscripts outside of parentheses and don’t change ANYTHING inside) Rewrite with subscripts Reduce/simplify (if needed)

Practice Time! Name  Formula NaCl Sodium chloride Aluminum hydroxide Iron (III) oxide Al(OH)3 Fe2O3

Helpful Hints for Ionic Compounds When determining the Roman numeral for a transitional metal, try to reverse crisscross first. If the subscript doesn’t match the charge of the known nonmetal, then it must have been simplified. When it doesn’t match, do a little trial and error. Double check your work by going the opposite way (determining formula from name) and see if your results match what you started with. Always put parentheses around polyatomic ions so you remember to “protect” them. You CANNOT change the subscripts of the polyatomic ions, so using parentheses will help you to remember that!

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