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Names & Formulas Nomenclature Over 6 million compounds have been identified. Each one has a unique name and formula. All compounds are neutral. I. 3 Categories of Compounds 1) Ionic: Used to name ionically bonded atoms. Made up of metals plus non-metals. 2) Molecular: Used to name covalently bonded atoms. Made up of non-metals. 3) Acids and Bases: All traditional acids begin + with the hydrogen ion (H ). All traditional bases end with hydroxide ion (OH ). II. Ionic Compounds Contain IONIC bonds. Form between metals and nonmetals. Ions combine in small, whole number ratios. They are ALWAYS NEUTRAL A. Binary Ionic Compounds “Binary” means two. Binary ionic compounds contain only two elements. Their names always end in “ide”. Writing Formulas of Binary Ionic Compounds 1. Write + and - ions. 2. Reduce oxidation numbers if needed. 3. “Criss-cross” oxidation numbers (without signs) to become subscripts within the formula Example #1 sodium chloride First, write the ions: Na+1 + Cl-1 Next, write the formula by crisscrossing oxidation numbers so that they become the subscripts of the other ion: Na1Cl1 Formula is NaCl Example #2 Calcium chloride First, write ions: Ca+2 + Cl-1 Next, criss cross oxidation numbers without signs to become subscripts within formula: Ca1Cl2 CaCl2 Example #3 Magnesium nitride +2 -3 Write ions: Mg + N Criss-cross Mg3N2 Naming Binary Ionic Compounds Cations (+) retain the name of the element. Anions (-) keep the root name but add “ide” ending. Example #1 LiF lithium fluoride Example #2 SrCl2 strontium chloride Example #3 Al2O3 aluminum oxide B. Multi-Charge Metals Most of the transition metals have variable oxidation numbers. Roman numerals are used to indicate charges of these elements. First, look at the total negative charge of the anion (oxidation number x number of atoms). Then, use this information to determine the oxidation number of the metallic cation. Example #1 FeO First, look at anion to determine total negative charge: -2 (oxidation #) x 1 (# of atoms) = -2 Total positive charge must be +2 because all molecules are neutral. When you look at formula, you see the ratio of Fe to O is 1:1 Fe2+ + O2iron (II) oxide Example #2 Fe2O3 Total charge on anion: -2 x 3 = -6 Total charge on cation: +6 ? x 2 = +6 ? = +3 Fe3+ + O2iron(III) oxide Example #3 Copper (I) Oxide Cu1+ + O2Cu2O These are easy because the Roman numeral in the name gives you the charge of the cation! Example #4 Copper (II) Oxide Cu2+ + O2CuO IMPORTANT EXCEPTIONS to MEMORIZE! Silver always forms a +1 ion. Zinc always forms a +2 ion. Cadmium always forms a +2 ion. The oxidation numbers of lead and tin also vary. STOP Do Binary Ionic Compounds HW Ternary Ionic Compounds C. Ternary Ionic Compounds Contain three or more elements Contain at least one polyatomic ion Writing Formulas and Naming Ternary Ionic Compounds Follow the same rules and complete the same steps as for binary ionic compounds Enclose PAI in parentheses when necessary Example #1 Aluminum phosphate Write ions: Al 3+ + PO4 3- Reduce oxidation numbers then criss-cross: Al1 (PO4 )1 AlPO4 Example #2 Sodium sulfate Na 1+ + SO4 Na2SO4 2- Example #3 Iron (II) bromate Fe2+ + BrO3Fe3(BrO)2 Example #4 CaCO3 calcium carbonate Example #5 Cu(NO3)2 Remember copper is a transition metal! copper(II) nitrate Example #6 (NH4)3N ammonium nitride STOP Do Ternary Ionic Compounds HW Molecular Compounds III. Molecular Compounds •Contain COVALENT bonds. •The same elements can combine in various ways. •PREFIXES are used to tell them apart. A. Binary Molecular Compounds Binary compounds contain two different elements. Binary compounds always end in “ide” . We will only learn BINARY molecular compounds. Prefixes: 1 = mono 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa 7 = hepta 8 = octa 9 = nona 10 = deca To name: Use prefixes on first atom, except for “mono”. Always use prefixes on the last atom. Change ending to “ide”. Examples S2O3 is disulfur trioxide CO is carbon monoxide OF2 is oxygen difluoride To write formulas: Look at prefixes attached to each element to determine subscript. Examples: Arsenic pentiodide = ArI5 Carbon dioxide = CO2 Diphosphorus trioxide = P2O3 B. Hydrocarbons Molecular compounds that contain only carbon and hydrogen Alkanes have single bonds Alkenes have double bonds Alkynes have triple bonds Alkanes carbon chain held together with single bonds. Generic Formula: CxH(2x + 2) Naming Alkanes Based on number of carbons in molecule (prefixes indicate #) All end in “ane”. Prefixes for Alkanes Meth = 1 Eth = 2 Prop = 3 But = 4 Pent = 5 Hex Hept Oct Non Dec = = = = = 6 7 8 9 10 Mice Eat Peanut Butter Meth Eth Prop But Examples Ethane is C2H6 Heptane is C7H16 STOP Do Molecular Compounds And Hydrocarbons HW IV. Acids and Bases Acids are easy to recognize because they begin with “H”. Bases are easy to recognize because they end with “OH” . A. Bases The anion in bases is always the hydroxide ion. Because they are ionic, you already know how to name them (there are no special rules) Examples NaOH sodium hydroxide KOH potassium hydroxide B. Binary Acids Have only two elements: hydrogen and a nonmetal. Naming Binary Acids 1)Use the prefix “hydro” 2) Add the suffix “ic” Examples: HCl is hydrochloric acid H3N is hydronitric acid To write formulas: +1 H 1) Start with 2) End with negative ion (nonmetal) from periodic table 3) “Criss-Cross” Examples: Hydroiodic acid = HI Hydrophosphoric acid = H3P C. Ternary Acids Have at least three elements: H and a polyatomic ion Naming Ternary Acids 1) DO NOT use “hydro” prefix! 2) Add suffix: if “ate” ion, use “ic” suffix if “ite” ion, “ous” suffix Examples #1 HClO3 ClO31- is chlorate (ate = ic) chloric acid Example #2 H2SO3 SO32- is sulfite (ite = ous) sulfurous acid To write formulas: 1) Start with H 1+ 2) End with negative polyatomic ion 3) “Criss-Cross” Examples: perchloric acid (ic = ate) Perchlorate is ClO4-1 All acids start with H+1 HClO4 chlorous acid (ous = ite) Chlorite is ClO2-1 All acids start with H+ HClO2 STOP Do Names and Formulas Of Acids HW