Naming and Writing Formulas for Ionic Compounds

Learn to name and write formulas for ionic compounds!

Naming Ionic Compounds Watch the following video and take notes on how to name ionic compounds. Ion naming rules AKA the "Stock System" Cations: Positive elements keep their names and end with "ion". If metal charge is unknown, report the charge in Roman numerals. Fe3+becomes iron (III) ion. Zn2+ becomes zinc ion.Anions: For elements, change ending to -ide. For polyatomic ions, just write the name.Chlorine (Cl) becomes chloride (Cl1-).Sulfur (S) becomes sulfide (S2-).Ammonium nitrate becomes NH4NO3 Name that ion! N3- nitride Na1+ sodium ion Se2- selenide Co6+ cobalt (VI) ion Br1- bromide Ni2+ nickel (II) ion Ag1+ silver ion Most Common Polyatomic Ions Use the Polyatomic Ion Cheat Sheet. acetate (condensed version) C2H3O21- chlorate ClO31- sulfate SO42- phosphate PO43- acetate CH3COO1- carbonate CO32- ammonium NH41+ nitrate NO31- hydroxide OH1- cyanide CN1- Formula to Name Guided Practice Following rules below1) Write down name of cation-positive element always goes first(if you do not know the charge then you have to find it and put in Roman numerals)2) Write down anion (change ending to -ide unless polyatomic ion)3) Combine into your name.Example 1: BaF2What is the cation in this compound? (it's common name) BariumWhat is the anion in this compound? (element with -ide ending) FluorideName of Compound: Barium FluorideExample 2:SnO2What is the cation in this compound? (IUPAC name with roman numeral) Tin (IV)What is the anion in this compound? (element with -ide ending) OxideName of Compound: Tin (IV) OxideExample 3: CsClO3What is the cation in this compound? (it's common name) CesiumWhat is the anion in this compound? (polyatomic ion) ChlorateUncriss-cross and see if the charges make sense!Name of Compound: Cesium chlorate Formula Is charge known? (Write yes or no) If not Roman numerals! Name Ag2CO3 yes silver carbonate PbO2 Find charge: Pb + 2(2-) = 0 no lead (IV) oxide SnF2 no tin (II) fluoride Cd(ClO3)2 yes cadmium chlorate Ga2(SO4)3 yes gallium sulfate TlCl no thallium (I) chloride Name to Formula Guided Practice Follow the rules below1) Identify cation and anion!(cation with Roman numeral tells you the charge)2)Find the least common multiple of the charges and make the charges add up to zero.(only multiple polyatomic ions appear in parentheses with the subscript on the outside i.e. Sr(NO3)2vs NaNO3)3) Show your check to make sure they add up to zero.4) Write final formula (Subscripts of 1 are not written i.e. NaCl). Example 1: copper (II) phosphate Identify the cation (symbol and charge--number first) Positive charge from Roman numeral Cu2+ Identify the anion (symbol and charge--number first) PO43- Least common multiple of charges (3 and 2 both go into...) 6 Number needed of cation (2 times _ makes 6) 3 Number needed of anion (3 times _ makes 6) 2 Show check (Space after each sign and equals!) Notice that both charges end up being LCM 6+ 6- = 0 Final Formula (do not include subscripts of 1) Charges are left out since they add up to zero. Cu3(PO4)2 Example 2 calcium carbonate Identify the cation (symbol and charge--number first) Ca2+ Identify the anion (symbol and charge--number first) CO32- Least common multiple of charges 2 Number needed of cation 1 Number needed of anion 1 Show check 2+ 2- = 0 Final Formula CaCO3 Example 3 silver sulfide Identify the cation (symbol and charge--number first) Ag1+ Identify the anion (symbol and charge--number first) S2- Least common multiple of charges 2 Number needed of cation 2 Number needed of anion 1 Show check 2+ 2- = 0 Final Formula Ag2S Example 4 thallium (III) acetate Identify the cation (symbol and charge--number first) Tl3+ Identify the anion (symbol and charge--number first)Write condensed version of acetate C2H3O21- Least common multiple of charges 3 Number needed of cation 1 Number needed of anion 3 Show check 3+ 3- = 0 Final Formula Tl(C2H3O2)3 Name to Formula Practice zinc cyanide Zn(CN)2 barium hydroxide Ba(OH)2 iron (II) chloride FeCl2 sodium fluoride NaF aluminum phosphate AlPO4 ammonium sulfate (NH4)2SO4 lithium hydride LiH chromium (IV) oxide CrO2 cadmium sulfide CdS