ClO 3. ClO -1 ClO 2. ClO 4

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1 Chemical Composition and Naming Summary Sheet 5* (*with a big thanks to Science Geek) vocabulary oxidation number = the number of electrons an element will give, take or share when a compound is formed chemical formula = a shorthand way of representing the types and numbers of atoms involved in a molecule or compound. Ionic compounds=the simplest ratio of cations to anions. variable oxidation state = elements in the d block can form compounds in a variety of ways because of the similar energy level of the s and d sublevels empirical formula = the smallest whole number ratio of atoms in a compound hydrate = a type of crystal that includes molecules of water as a part of its structure Naming Ions I. Monatomic Ions A. Ions formed from a single atom B. Naming Monatomic Ions 1. Monatomic cations are a. Identified by the element s name 2. Monatomic anions a. Drop the ending of the element name b. Add an ide ending II. Polyatomic Ions A. Oxyanions 1. Polyatomic anions that contain oxygen B. Naming a series of similar polyatomic ions ClO ClO 2 ClO 3 ClO 4 Hypochlorite Chlorite Chlorate Perchlorate Naming and Writing Formulas for Ionic Compounds I. Oxidation Numbers A. oxidation numbers in a compound show how many electrons are exchanged in a relationship, the total of the oxidation numbers in a compound must add up to zero (polyatomic ions add up to their charge). B. oxidation numbers rules ALWAYS uncombined elements/pure elements = 0 group 1 metals = +1 group 2 metals = +2 fluorine = least electronegative atom is assigned a +charge most electronegative atom is assigned a charge USUALLY oxygen =-2 ( peroxides ) superoxides /2, with halogens +2 hydrogen = +1 ( with group 1 or 2 metals ) use the always rules first, the usually rules second, and judge everything else by what it is connected to

2 II. Binary Ionic Compounds A. Compounds composed of two different elements B. Naming Binary Ionic Compounds from Their Formulas 1. Write the name for the cation (always come first) 2. Write the name for the anion C. The Stock System of Nomenclature 1. Roman numerals are used to denote the charge of metals that can form two or more cations. 2. The numeral is enclosed in parentheses and placed immediately after the metal name a. Iron(II) and Iron(III), pronounced iron two and iron three 3. Roman numerals are never used: a. For anions b. For metals that form only one ion D. Writing Formulas for Binary Ionic Compounds 1. Write the symbols for the ions side by side. ALWAYS write the cation first! 2. Cross over criss-cross-applesauce-the charges using their absolute values (make the superscript of on element/polyatomic ion the subscript for the other element/polyatomic ion 3. Cross over the charges by using the absolute value of each ion s charge as the subscript for the other ion 4. Check that the subscripts are in smallest whole number ratio E. Naming compounds containing polyatomic ions 1. Same as for monatomic ions F. Writing formulas including polyatomic ions 1. Use parentheses when you need MORE THAN one of a polyatomic ion 2. Parentheses are NEVER used for monatomic ions, regardless of how many are in the formula Naming and Writing Formulas for Molecular Compounds I. Naming Binary Molecular Compounds A. Binary Molecular Compounds 1. Covalently bonded molecules containing only two elements, both nonmetals B. Naming 1. Least electronegative element is named first 2. First element gets a prefix if there is more than 1 atom of that element 3. Second element ALWAYS gets a prefix, and an -ide ending Examples: N 2 O 3 = dinitrogen trioxide CO = carbon monoxide, not monocarbon monoxide

3 Naming and Writing Formulas for Acids and Bases I. Naming Acids A. Binary Acids 1. Acids that consist of two elements, usually hydrogen and one of the halogens B. Oxyacids 1. Acids that contain hydrogen, oxygen and a third element (usually a nonmetal) C. Naming Acids 1. Types of Acids a. Monoprototic = acid has only one hydrogen b. Diprotic = acid has two hydrogens c. Triprotic = acid has three hydrogens d. Polyprotic = any acid having two or more hydrogens 2. Naming Binary Acids a. has only 2 elements a hydrogen and a non-metal b. prefix = hydro c. suffix = ic Examples: HCl hydro-chlor-ic acid HF hydro-flour-ic acid H 2 S hydro-sulur-ic acid 3. Naming Oxyacids a. An acid that contains at least one hydrogen, one oxygen and another nonmetal. b. Use the name of the central non-metal c. Suffix = change the ate suffix on the poly atomic ion to -ic d. Examples = HCLO 3 = chloric acid ClO 3 = chlorate H 2 SO 4 = sulfuric acid SO -2 4 = sulfate H 3 PO 4 = phosphoric acid PO -3 4 = phosphate e. other rules i. Prefix = per, suffix = ic if there is one more oxygen atom than in the ic version of the polyatomic ion ii. Suffix = -ous if the one less oxygen than in the ic version of the poly atomic ion iii. Prefix = hypo, suffix = -ous if there are 2 less oxygens than in the ic form of the polyatomic ion. Examples: HNO 3 nitric acid NO 3 =nitrate HNO 2 nitrous acid NO 2 = nitrite HClO hypochlorous acid ClO = hypochlorite HClO 2 Chlorous acid ClO 2 = chlorite HClO 3 Chloric acid ClO 3 = chlorate HClO 4 Percloric acid ClO 4 = perchlorate II. Naming Bases A. Bases are ionic compounds and are named in the same way as other ionic compounds

4 The Laws Governing Formulas and Names I. The Law of Definite Proportions In samples of any chemical compound, the masses of the elements are always in the same proportions. Translation: Each compound has a definite, unchanging chemical formula. Percent Composition and Chemical Formulas I. Percentage Composition A. Percentage Composition 1. The percentage by mass of each element in a compound B. Hydrates 1. Crystalline compounds in which water molecules are bound in the crystal structure Copper (II) sulfate pentahydrate CuSO4 5H2O a. The raised dot means "Water is loosely attached" It does NOT mean multiply when determining formula weight II. Empirical Formula (Theoretical) A. Definition: The symbols for the elements combined in a compound, with subscripts showing the smallest whole-number ratio of the different atoms in the compound B. Calculation of Empirical Formula 1. Assume a 100 g sample of the compound 2. Treat % as grams 3. Convert grams to moles using molar mass of each element 4. Place each mole quantity in ratio to the smallest number of moles a. Construct element ratios from the nearest resulting whole numbers III. Molecular Formula (Actual lab based data used) A. Definition A formula for a molecular compound that represents ALL of the atoms found in a single molecule of that compound The molecular formula is either the same as the empirical formula, or it is a whole number multiple of the empirical formula B. Calculation of Molecular Formula 1. Necessary Information a. Empirical Formula b. Molecular mass 2. Calculations a. (empirical formula wt.) x = molecular weight b. (empirical formula) x = molecular formula

5 NAMING FLOW CHART only 2 elements in the compound? no yes look for polyatomic ion binary compound negative polyatomic only? 2 nonmetals? no yes no yes polyatomic + nonmetal-ide prefix system_ metal has > 1 ox. state? metal has > 1 ox. state? no yes no yes metal + polyatomic metal + nonmetal-ide_ metal-(roman numeral) + polyatomic or -ic/-ous + polyatomic metal-(roman numeral) + nonmetal-ide or -ic /-ous + nonmetal - ide