Naming and Formula Writing

A Quick Review of Ions Cations Anions Transition Metal Ions Polyatomic Ions (Table E)

Cations Metallic elements tend to LOSE electrons and become positively charged Group 1A: loses one electron  become +1 Group 2A: lose two electrons  become +2 Group 3A: lose three electrons  become +3

Anions Non-metals tend to gain electrons and become negatively charged RULE: The charge of any ion of a Group A nonmetal is determined by subtracting 8 from the group number. Example: Group 7A: -1 charge Group 6A: -2 charge Group 5A: -3 charge

Transition Metal Ions Many of the transition metals form more than one cation with different ionic charges Ex. Fe2+ and Fe3+

Transition Metal Ions Stock System: A roman numeral is used to indicate the positive oxidation state ONLY for an element that can have more than one possible state Example: Fe2+ iron (II) Fe3+ iron (III)

Polyatomic Ions (Table E) Tightly bound atoms that behave as a unit and carry a charge Ex: SO42- , HPO42- The names of most polyatomic ions end in –ite or –ate

Types of Compounds Binary Compounds: Any combination of two elements Ex: NaCl, H2O, SF6 Tertiary Compounds: Any combination of three different elements Ex: KClO3, H3PO4, (NH4)2S Quaternary Compounds: Any combination of four different elements Ex: NaHCO3, (NH4)3PO4

Binary Compounds Binary Compounds can be either Ionic: metal and non-metal Ex) NaCl, FeO, BaF2 2) Covalent: non-metal and non-metal Ex) SO2, PCl3

Binary Ionic Compounds To identify an ionic compound, look for a metal and a nonmetal Metal = cation Non-metal = anion Examples: KCl, MgCl2, CaO, LiBr

Naming Binary Ionic Compounds 1) Name the cation first When naming the cation, do not change the name of the metal 2) Name the anion second When naming the anion, keep the root of the element name and change the ending to –ide ***No prefixes!!! Ex) NaCl vs. CaCl2

Practice- Binary Ionic Compounds (ex) BeCl3 beryllium chloride (ex) KF potassium fluoride (ex) MgO magnesium oxide (ex) Na2S sodium sulfide (ex) CaCl2 calcium chloride

Ionic Compounds with Polyatomic Ions For polyatomics, DO NOT change the ending to –ide, keep what is on Table E. (ex) NaOH sodium hydroxide (ex) LiNO3 lithium nitrate (ex) KMnO4 potassium permanganate (ex) NH4Cl ammonium chloride (ex) NH4OH ammonium hydroxide

Ionic Compounds with Transition Metals Use Roman Numerals ONLY if there is a metal with more than one ox # listed on the PT ex) Cu2O vs. CuO copper (I) oxide vs. copper (II) oxide (ex) Fe2O3 vs. FeO iron (III) oxide vs. iron (II) oxide

More Transition Metal Ion Practice 1) Cu2O copper (I) oxide 2) CrCl3 chromium (III) chloride 3) FeCl2 iron (II) chloride 4) CuSO4 copper (II) sulfate 5) MnBr3 manganese (III) bromide

Writing Formulas for Ionic Compounds 1) Determine the charges on the cation and anion If there is a roman numeral in the name, it tells you the charge of the first element Ex. iron (III) oxide  Ending of –ate or –ite indicates a polyatomic ion  check charges on RT

Writing Formulas for Ionic Compounds 2) Use the cross-over method to determine the subscripts from the charges Example: Lithium Sulfide Li2S 3) Reduce subscripts to the smallest whole numbers Example: Magnesium Oxide  MgO ** Do not reduce the subscripts of polyatomic ions!

Formulas for Ionic Compounds with PAIs Use parentheses around polyatomic ions ONLY if there is more than one Examples: ammonium chloride  NH4Cl ammonium phosphate  (NH4)3PO4 magnesium nitrate  Mg(NO3)2 copper (II) phosphate  Cu3(PO4)2

Write the formula for: Magnesium hydroxide  Mg(OH)2 Tin (II) nitrate  Sn(NO3)2 Nickel (II) acetate  Ni(C2H3O2)2 Sodium chromate  Na2CrO4 Aluminum permangate  Al(MnO4)3 Magnesium phosphate  Mg3(PO4)2 Mercury (II) carbonate  HgCO3 Copper (I) sulfate  Cu2SO4

How to Identify a Binary Covalent Compound Non-metal to non-metal Example: CO2, HF, CH4 The less electronegative element usually comes first

Naming a Binary Covalent Compound Use the prefix system Mono = one Di = two Tri = three Tetra = four Penta = five Hexa = six Hepta = seven Octa = eight Deca = ten

Naming Binary Covalent Compounds Name first element. Only use a prefix if there is more than one. Always use a prefix to tell how many of the second element there are and change the ending of the second element to –ide. If the prefix ends in an “o” or an “a”, these letters are dropped for oxygen (ie. 1 oxygen is monoxide, NOT monooxide)

Practice (ex1) NO nitrogen monoxide (ex2) N2O4 dinitrogen tetroxide (ex3) PF5 phosphorus pentafluoride (ex4) XeF4 xenon tetrafluoride (ex5) CCl4 carbon tetrafluoride

Writing the Formula of a Covalent Compound Convert the prefixes from the name into subscripts in the formula Example: dinitrogen pentoxide  N2O5 Do not write a subscript of “1” Example: nitrogen monoxide  NO

Practice (ex1) tetraiodine heptoxide I4O7 (ex2) sulfur trioxide SO3 (ex3) phosphorus pentafluoride PF5 (ex4) nitrogen trifluoride NF3 (ex5) disulfur dichloride S2Cl2

Naming Acids Acids are a group of compounds that produce H+ ions (hydronium ions) when dissolved in water Chemical formula of acids is generally HnX n = number of hydrogen ions X = anion

Naming Acids If the acid is binary (contains hydrogen and one other element), start with the prefix hydro- followed by the root of the anion and the suffix –ic, and add the word acid. hydro_______ic acid Ex. HCl hydrochloric acid HI hydroiodic acid H2S hydrosulfuric acid

Naming Acids 2) If the acid contains a polyatomic ion, start with the root of the central atom in the polyatomic ion and add the appropriate suffix followed by the word acid. Suffix: ate  ic ite  ous Ex. H2SO4 H2SO3 HNO3 HNO2

Writing Formulas for Acids Use the rules for writing the names of acids in reverse to write the formulas for acids. Be sure that the charges cancel!!! Ex. hydrobromic acid HBr Ex. Phosphoric acid H3PO4 Ex. hydroiodic acid HI Ex. Hypochlorous acid HClO2 Ex. Sulfurous acid H2SO3 Ex. Carbonic acid H2CO3

Bases A base is an ionic compound that produces OH- ions (hydroxide ions) in water Use the rules for ionic compounds! (nothing new) Ex) NaOH sodium hydroxide Ca(OH)2 calcium hydroxide LiOH lithium hydroxide magnesium hydroxide Mg(OH)2 potassium hydroxide KOH

Summary An –ide ending generally indicates a binary compound An –ite or –ate means a polyatomic ion that includes oxygen in its formula Prefixes in a name indicate the compound is molecular A Roman numeral after the name of a cation shows the ionic charge of the cation