Naming and Formula Writing IONIC COMPOUNDS Naming and Formula Writing

Monatomic Ions

Predicting Charges on Monatomic Ions KNOW THESE !!!! +1 +2 -3 -2 -1 0 Cd+2

Naming Positive Ions Before you name an Ion you have to know the charge Group 1 = always +1 Group 2 = always +2 Aluminum = always +3 Zinc and Cadmium = always +2 Silver = always +1

Naming Positive Ions With group 1, 2, Al, Zn, Cd, and Ag you just give the name of the atom Na+ is Sodium Mg+2 is Magnesium Ag+ is Silver Al+3 is Aluminum

Naming Negative Ions All negative ions have their endings changed to –ide Oxygen becomes oxide Fluorine becomes Fluoride Nitrogen becomes Nitride Chlorine becomes Chloride

Formulas of Ionic Compounds Formulas of ionic compounds are determined from the charges on the ions atoms ions     - Na  +  F  Na+ F  NaF     sodium + fluorine sodium fluoride formula Charge balance: 1+ 1- = 0      

Writing a Formula Write the formula for the ionic compound that will form between Ba2+ and Cl To cancel out Ba’s +2, then two -1 Cl’s are needed! Solution: 1. Balance charge with + and – ions 2. Write the positive ion of metal first, and the negative ion Ba2+ / Cl Cl 3. Write the number of ions needed as subscripts BaCl2

Balancing a formula by math Every ionic compound should have a formula that has a charge that equals zero Barium Fluoride Ba+2 F- How many F ’s are needed to balance Ba+2 ? Two So, the Formula is BaF2 -

Another way – Drop, Swap, Reduce What is the formula for Aluminum Oxide? Al is always +3 Oxide is always -2 Al+3, O-2 DROP: Al3O2 SWAP: Al2O3 REDUCE: 2 and 3 are lowest integers, so leave alone The Final Formula is Al2O3 Also called “Cris—Cross”!

Another example Magnesium Oxide Mg is +2 Oxide is -2 Mg+2, O-2 DROP: Mg2O2 SWAP: Mg2O2 REDUCE: MgO, 2 and 2 divide each other out The Final Formula is MgO

Learning Check Which is the correct formula for the compounds containing the following ions: 1. Na+, S2- a) NaS b) Na2S c) NaS2 2. Al3+, Cl- a) AlCl3 b) AlCl c) Al3Cl 3. Mg2+, N3- a) MgN b) Mg2N3 c) Mg3N2

Solution 1. Na+, S2- b) Na2S 2. Al3+, Cl- a) AlCl3 3. Mg2+, N3- c) Mg3N2

CaCl2 = calcium chloride Naming Compounds Binary Ionic Compounds: 1. Cation first (+), then anion (-) 2. Monatomic cation = name of the element Ca2+ = calcium ion 3. Monatomic anion = root + -ide Cl- = chloride CaCl2 = calcium chloride

Naming Binary Ionic Compounds Examples: NaCl ZnI2 Al2O3 sodium chloride zinc iodide aluminum oxide

Learning Check Complete the names of the following binary compounds: Na3N sodium ________________ KBr potassium ________________ Al2O3 aluminum ________________ MgS ________________________

Transition Metals Elements that can have more than one possible charge MUST have a Roman Numeral to indicate the charge on the individual ion 1+ or 2+ 2+ or 3+ Cu+, Cu2+ Fe2+, Fe3+ copper (I) ion iron(II) ion copper (II) ion iron(III) ion ROMAN NUMERALS: I = one II = two III = three IV = four…

Names of Variable Ions FeCl3 (Fe3+) iron (III) chloride These elements REQUIRE Roman Numerals because they can have more than one possible charge: anything except Group 1A, 2A, Ag, Zn, Cd, and Al (You should already know the charges on these!) Or another way to say it is: Transition metals and the metals in groups 4A and 5A (except Ag, Zn, Cd, and Al) require a Roman Numeral FeCl3 (Fe3+) iron (III) chloride CuCl (Cu+ ) copper (I) chloride SnF4 (Sn4+) tin (IV) fluoride PbCl2 (Pb2+) lead (II) chloride Fe2S3 (Fe3+) iron (III) sulfide

Learning Check Complete the names of the following binary compounds with variable metal ions: FeBr2 iron (_____) bromide CuCl copper (_____) chloride SnO2 _____(_____ ) ____________ Fe2O3 ________________________ Hg2S ________________________

Polyatomic Ions Some ions are composed of more then one atom These are called polyatomic ions Poly = more

Formulas and names Nitrate = NO3- Sulfate = SO4-2 Silver nitrate Ag+ NO3- AgNO3 Copper (I) Sulfate Cu+ SO4-2 Cu2SO4

More Polyatomics Lead (IV) Phosphate Pb+4 PO4-3 Pb3(PO4)4 Notice: When more then one Polyatomic is present you surround it with () Notice: The subscripts on Polyatomic ions are NEVER changed

Learning Check Write the correct formula for the compounds containing the following ions: 1. Na+, PO4-3 a) NaPO4 b) Na2PO4 c) Na3PO4 2. Al3+, NO3- a) Al(NO3)3 b) AlNO3 c) Al3NO3 3. NH4+, N3- a) NH4N b) NH4N c) (NH4)3N

Answers 1. Na+, PO4-3 c) Na3PO4 2. Al3+, NO3- 3. NH4+, N3- a) Al(NO3)3 c) (NH4)3N

Polyatomic Ions you have to know NAME FORMULA Acetate C2H3O-1 Carbonate CO3-2 Chlorate ClO3-1 Cyanide CN-1 Hydroxide OH-1 Nitrate NO3-1 Peroxide O2-2 Phosphate PO4-3 Sulfate SO4-2 Ammonium NH4+1

More on Polyatomics Most polyatomic ions end in –ate The ending –ite means one less oxygen is present then in the ending –ate Example: Nitrate versus Nitrite: NO3- NO2- NOTICE: Only the number of O’s changed, not the charge!

Properties of Ionic Compounds Ionic compounds are: also known as salts They are usually hard and brittle Conduct electricity when molten or dissolved Have very high melting and boiling points Most are soluble in water Normally composed of at least one metal and one nonmetal