Chapter 9 Naming Compounds and Writing Formulas Ionic Compounds; Molecular Compounds and Acids Types of Compounds CompoundFormed when atoms of two or more elements combine CHEMICALLY. Law of Definite ProportionsIn ANY CHEMICAL compound the elements always combine in the same proportion by mass. This agrees with Dalton’s Atomic Theory that atoms combine in small whole # ratios. Molecular Compounds Two Types of Compounds1. Molecular Compounds 2. Ionic Compounds 1. Molecular Compounds Formed between 2 or more NONMETALS (Covalent Bond- Share Electrons) - Liquid or gas at room temp. and have relatively low melting and boiling points. Molecule MoleculeNEUTRAL no charge, group of atoms that act like a unit (one thing) Molecules of a compound are all identical to each other Molecules of different compounds are different. Ex: CO2 (1C : 2 O); CO (1C : 1O) Molecular Formula Tells the number and kinds of atoms in a molecule of a compound. (CO2 & CO) Nonmetal + Nonmetal Covalent Bond: Share Electrons Diatomic molecules: 7 nonmetallic elements that are always paired and exist a molecules NOT atoms. MEMORIZE: H O N Cl Br I F Hydrogen H2; Oxygen O2; Nitrogen N2; Chlorine Cl2; Bromine Br2; Iodine I2; Fluorine F2 Ionic Compounds - Metal + Nonmetal - Made up of IONS - Relatively high melting and boiling points - NEUTRAL (ion charges cancel out; total + charge = total – charge) ION Atom or group of atoms that have an UNEQUAL number of protons and electrons (#p+ does NOT = #e-) have a + or – charge Cations- atom or group of atoms with + charge Metals Lose electrons When naming cations the name stays the same as the element. EX: Na+ = sodium ion; Al+3 = aluminum ion Cation Charges ionic charges of Group A metals (see front of periodic chart) ionic charges of Group B metals (transitional metals) – see back of periodic chart Roman Numerals – are used to indicate the charge of a transitional metal. Examples: Copper I = Cu +; Copper II = Cu+2 Lead II = Pb+2; Lead IV = Pb+4 Anions Atom or group of atoms with a – charge Nonmetals Gain electrons When naming anions the ending changes to “ide” Ex: chlorine becomes chloride (Cl-); oxygen becomes oxide(O-2); nitrogen becomes nitride (N-3) Polyatomic Ions Tightly bound group of atoms that act as a unit (one thing) and carry a charge. Also called Radicals Most end in “ite” or “ate”; “ite” ending has one less oxygen than “ate” ending. Examples; chlorite ClO2-1; chlorate ClO3-3 Except: hydorxide (OH-); cyanide (CN-); ammonium (NH4+). Hypo – means 1 less oxygen (hypodermic means under the skin) hypochlorite ClOPer – means 1 more oxygen perchlorate ClO4- Formula Unit (FU) Lowest whole number ration on IONS in an ionic compound. - Ionic Compounds are NOT MOLECULES they are called Formula Units. Chemical Formula shows the kinds and number of atoms in the SMALLEST UNIT of a compound. The most positive element (metallic) is written first. EX: H2O = 2 Hydrogen atoms + 1 Oxygen atoms CO2 = 1 Carbon atom + 2 Oxygen atoms Homework Questions What are the differences between an ionic compound and molecular compound? (3) Answer: Ionic- made up of ions; metal + nonmetal; High BP & MP; Formula Unit Molecular- made up of nonmetals; share electrons covalent bonds; usually liquids or gases at room temp.; Molecules Homework Questions Why aren’t ionic compounds molecules? Ionic Compounds are Formula Units (FU’s) and molecules are made up of 2 or more nonmetals What is the smallest ratio of an ionic compound called? Formula Unit (FU) Name the 7 diatomic elements and write their formulas correctly. Hydrogen; H2 Oxygen; O2 Nitrogen; N2 Chlorine; Cl2 Bromine; Br2 Iodine; I2 Fluorine; F2 Homework Questions cont. Metals form + ions called ___________. Nonmetals form - ions called _______. What group of metals have more than one possible charge? Group B metals; transitional metals What is a polyatomic ion? A group of atoms that act as a single unit and carry a charge. Naming compounds and Writing Formulas Binary compoundSimplest compound made up of 2 elements Examples: [ Sodium chloride – NaCl ] [iron II chloride – FeCl2 ] (NAMING) 1.) element with the positive ionic charge is written first. ( metals ) Group A Metals – metal name is written. Example Na+ = sodium Group B Metals ( Transitional ) – Roman Numeral Indicates the charge. Examples : Fe+2 = Iron II Mercury I Hg+ = ____________ Tin IV Sn+4 = ____________ ** Use the back of your periodic chart (Common Metal Ions with more than 1 ionic charge!) 2.) element with the negative ionic charge is written next. ( nonmetal ) Change the ending of the nonmetal to ( ide ) Nonmetal marries the metal and changes its name to “ide” like a bride. Examples: chlorine – chloride bromide Bromine - ________________ oxide Oxygen - ________________ USE THE RULES ABOVE TO NAME THE BINARY IONIC COMPONDS BELOW: Magnesium oxide 5.) FeCl3 ____________ Iron III chloride 1. MgO______________ Barium Sulfide Tin IV bromide 2. BaS ______________ 6.) SnBr4 ____________ Sodium nitride phosphide 3. Na3N _____________ 7.) K3P Potassium ____________ Copper I oxide 4. Cu2O _____________ 8.) PbS Lead II sulfide ____________ WRITING FORMULAS 1.) write the ion for the metal first Group A Metals –Examples: Lithium – Li + +3 Al Aluminum - ___ +2 Mg Magnesium - ___ +1 Rb Rubidium - ___ Group B Metals – The Roman Numeral indicates the charge Examples: Tin II – Sn+2 Copper I - Cu+1 ____ Hg+2 Pb+4 Mercury II - ____ Lead IV - ____ write the ion for the non-metal Group VA, VIA, VIIA The number of the charge = 8 – the groupA number Examples: sulfide = 8 – 6 = 2 -3 P phosphide = ______ I Iodide = _____ ion = S-2 Cross-Over-Method Place the charge number of the metal as the subscript to the nonmetal and the charge number of the nonmetal as the subscript to the metal. You must reduce the charges if you can. Examples: Lithium Fluoride Li+ F- = LiF Magnesium Fluoride + -2 Potassium Sulfide K S = K2S Mg+2 F- =MgF2 + Copper I Chloride Cu Cl = CuCl Aluminum Nitride Al+3N-3 = AlN Chromium III Sulfide Cr+3 S-2 = Cr2S3 USE THE RULES ABOVE TO WRITE FORMULAS FOR THE BINARY IONIC COMPOUNDS: Calcium Fluoride __________ Ca+2 F- = Rubidium Iodide ___________ Rb+ I- = CaF2 RbI +P3 Na Sodium Phosphide ________ Strontium chloride__________ Sr+2 Cl- = Na3P SrCl2 Mercury I Oxide ___________ Hg+ O-2 = Tin II Sulfide______________ Sn+2 S-2 = Hg2O SnS Fe+3 N-3 = Iron III nitride _____________ Copper I Selenide___________ Cu+ Se-2 = FeN Cu2Se Classwork and homework worksheet 2 & 3 Binary Ionic Compounds. Ternary Compounds Ionic and Ternary Compounds are _________ Polyatomic Ion contain a _____________________. POLYATOMIC ION – A group of atoms that act as a single unit and carry a charge. Polyatomic ions end in “ ite “ or “ ate“ EXCEPTIONS: (OH)- hydroxide (CN)- cyanide *only (+) poly atomic ions (NH4)+ ammonium (PH4)+ phosphonium (Naming) Rules are similar to Binary ionic compounds. Element with positive ionic charge is cation ) written first. ( Group A Metals: name simply written Ex. Ca2+ - calcuim Group B Metals: need a roman numeral Ex. Pb2+ _________ Lead II 2. Polyatomic ion ( radical ) written next. Write the name as it appears on the back of the Periodic Chart. Ex. (C2H3O2)- acetate (Cr2O7)2- dichromate Naming Examples: LiCO3 Lithium carbonate Be(CN)2 Beryllium cyanide Sn(SO4)2 Tin IV sulfate USE THE RULES ABOVE TO NAME THE TERNARY IONIC COMPOUNDS BELOW: Magnesium sulfate MgSO4 ___________________________ Sodium nitrate NaNO3____________________________ Calcium carbonate CaCO3 ___________________________ Sodium hydroxide NaOH __________________________ Barium chlorite Ba(ClO2)2 ________________________ Ternary Naming Continued Iron III tartrate Fe2(C4H4O6)3 __________________ Ammonium phosphate (NH4)3PO4 ________________________ Copper I chromate Cu2CrO4 __________________________ Mercury I nitrite Hg(NO2) __________________________ aluminum sulfate Al2(SO4)3 __________________________ Writing Ternary Ionic Formulas Write the ion for the metal first. – Group A Metals – Group # = charge Ex. Calcium Group 2 = Ca +2 Rubidium Group 1 = Rb +1 Boron Group 3 = B +3 Group B Metals – The Roman Numeral tells you the charge number. Ex. Iron III Fe +3 Lead IV Pb+4 Mercury I Hg +1 Tin II Sn +2 Write the polyatomic ion next (USE PARENTHESIS) *Remember polyatomic ions end in “ ite “ or “ ate “ except (OH)- hydroxide and (CN)- cyanide Examples: Sulfite SO3 -2 Carbonate CO3 -2 Phosphate PO4 -3 Nitrite NO2 - Cross-Over-Method write the charge number of the metal as the subscript of the polyatomic ion. (You MUST use PARENTHESIS if the subscript is 2 or greater but DO NOT use Parenthesis if the subscript is 1) 2. write the charge number of the polyatomic ion as the subscript of the metal. *You must reduce if you can but NEVER change the polyatomic ion!! DO NOT TOUCH THE POLYATOMIC ION !! DO NOT CHANGE THE DO NOT TOUCH THE POLYATOMIC ION DO NOT CHANGE THE FORMULA OF THE POLYATOMIC ION !! Examples: Magnesium nitrate Mg+2 NO3- = Mg(NO3)2 Aluminum sulfate Al+3 SO4-2 = Al2(SO4)3 Iron II sulfite Fe+2 SO3-2 = FeSO3 Iron III sulfite Fe+3 SO -2 = Fe (SO ) 3 2 3 3 Tin IV nitrate Sn+4 NO3- = Sn(NO3)4 USE THE RULES ABOVE TO WRITE TERNARY FORMULAS FOR THE COMPOUNDS +1;-2 (NH4)2S Ammonium sulfide __________________ +1;-2 Ag2CrO4 Silver chromate ____________________ +3;-2 Fe2(C4H4O6)3 Iron III tartrate _____________________ +2;-1 Be(OH)2 Beryllium hydroxide ________________ aluminum oxalate +3;-2 Al2(C2O4)3 _________________ +1;-1 CuCN Copper I cyanide ___________________ +2;-2 NiCO3 Nickel carbonate ___________________ Molecular Compounds Writing names and Formulas Molecular Compounds Made up of 2 or more NONMETALS (NO METALS or IONS) Share electrons when bonding Sharing Electrons is called COVALENT BONDING The smallest unit of a molecular compound is called a MOLECULE. (NAMING) To write the name, write 2 words 1.) the non-metal closest to the metals on the periodic chart is written first. 2.) Prefixes are used to tell how many atoms of each element are in the compound. –1 –2 –3 –4 –5 mono di tri tetra penta 6 hexa 7 hepta 8 octa 9 nona 10 deca Exception: don’t write mono- if there is only one of the first element. 3.) The second element always uses a prefix and ends in “ _ide ”. 4.)No double vowels when writing names (oa, oo) Ex. CO carbon monoxide CO2 carbon dioxide P2O5 diphosphorus pentoxide Name These N2O Dinitrogen monoxide NO2 Nitrogen dioxide Cl2O7 Dichlorine heptoxide CBr4 Carbon tetrabromide SiO2 silicon dioxide P2O3 Diphosphorus trioxide (FORMULA WRITING) NO CRISS CROSSING Examples: Phosphorous pentachloride - PCl5 Dinitrogen trisulfide – N2S3 NO3 Nitrogen trioxide _________ CF4 carbon tetrafluoride _______ I2Cl10 Diiodine decachloride _____ PI3 phosphorous triiodide ______ SBr6 Sulfur hexabromide _______ NF5 nitrogen pentafluoride ______ P2S3 Diphosphorous trisulfide ____ CBr4 carbon tetrabromide ______ Acids Writing names and Formulas Acids Compounds that give off hydrogen ions when dissolved in water. Must have H in them. will always be some H next to an anion. The anion determines the name. Naming acids If the anion attached to hydrogen is ends in -ide, put the prefix hydro- and change ide to -ic acid HCl - hydrogen ion and chloride ion hydrochloric acid H2S hydrogen ion and sulfide ion hydrosulfuric acid Naming Acids If the anion has oxygen in it it ends in -ate or -ite change the suffix -ate to -ic acid HNO3 Hydrogen and nitrate ions Nitric acid change the suffix -ite to -ous acid HNO2 Hydrogen and nitrite ions Nitrous acid Name these HF Hydrofluoric acid H3P Hydrophosphoric acid H2SO4 sulfuric acid H2SO3 sulfurous acid HCN hydrocyanic acid H2CrO4 chromic acid Writing Acid Formulas/Naming Hydrogen will always be first name will tell you the anion make the charges cancel out Starts with hydro- if no oxygen in the acid, -ide ending becomes –ic Ex. HCl = hydochloric acid no hydro, -ate ending from polyatomic ion becomes -ic, H2SO4 = sulfuric acid -ite ending becomes –ous, H2SO3 = sulfurous acid Write formulas for these hydroiodic acid acetic acid HI HC2H3O2 carbonic acid H2CO3 phosphorous acid hydrobromic acid H3PO3 HBr