Naming Chemical Compounds And above all these put on love, which binds everything together in perfect harmony. Col 3:14

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1 Naming Chemical Compounds And above all these put on love, which binds everything together in perfect harmony. Col 3:14 Introduction Chemical Compounds are placed into one of two categories, ionic compounds and molecular compounds. Ionic compounds are formed between a metal and a nonmetal or between a polyatomic ion and a nonmetal. Molecular compounds are formed between two or more nonmetals held together by covalent bonds. As they differ in the bonds that hold them, so too are they distinguished by their naming. In the lab Ions and Ionic Bond Puzzle, you practiced labeling the charges of ions of metals and nonmetals, reviewed polyatomic ions, and performed an exercise to predict the ratios in which metal anions and nonmetal cations combine. This knowledge is necessary in naming ionic compounds, particularly in going from the ionic compound name to its chemical formula. If necessary, review the information in that lab now. Oxidation numbers are assigned to elements within a compound and indicate the element s positive or negative nature. Oxidation numbers are needed to: A) write the chemical formula from the ionic compound name, and; B) assign the Roman Numeral on the transition metal cation for ionic compounds with variable oxidation numbers. Molecular compounds may be divided into three categories. Binary molecular compounds contain two nonmetals held by covalent bonds. Ternary molecular compounds contain more than two covalently bound nonmetals. Acids are compounds in which hydrogen is bound to either a nonmetal (a binary acid) or to a polyatomic acid (a ternary oxyacid). Given a formula can you recognize whether the compound is ionic or molecular? After learning how to name ionic and covalent compounds, it is imperative to be able to distinguish between them given either just the name or the formula. The final portion of this lab will be an exercise in putting all the information together. Learning Objectives: Proficiency in naming ionic and covalent compounds from the formula Competence in providing an ionic or covalent formula given the compound name Identify a compound as ionic or covalent Materials Required: From Chemistry Kit Student Supplied Periodic Table Text or Reference book, if desired Part 1 Ionic Compounds We will practice naming binary ionic compounds consisting of one metal and one nonmetal. We will also practice naming ternary ionic compounds which contain polyatomic ions (a group of more than one nonmetals held together by covalent bonds and holding a charge). Here is a 2016 Catholic Initiatives in Math and Science, LLC All Rights Reserved 1

2 short summary of the rules for naming, although more details may be found in your textbook or a reference book: The cation keeps its name and the anion uses the root name plus an ide ending. For example, Rb2O is named rubidium oxide. Metals with variable charges are written with Roman numerals following the name. For example, FeBr2 is named Iron(II) bromide. Polyatomic ions keep their names in naming ionic compounds in which they are present. For example, NH4F is ammonium fluoride and LiCN is lithium cyanide In compounds, each element has an oxidation number that indicates its positive or negative character. When going from the name to an ionic compound formula, oxidation numbers must be found so that the ratio of cation to anion may be determined. The oxidation number is the same as the charge on that atom. This is how the charge on iron in FeBr2 was determined, and the compound named Iron(II) bromide. Contrast that with charge determination on iron of FeBr3 and naming this ionic compound, Iron(III) bromide. (See the lab titled: Ions and Ionic Bond Puzzle.) Experiment Naming Ionic Compounds 1. Fill out the empty boxes in Table 1: Where there is a name, place the corresponding formula Where there is a formula, place the corresponding name. 2. Complete the questions under Part I: Data Analysis 3. Proceed to Part 2 Naming Molecular Compounds 2016 Catholic Initiatives in Math and Science, LLC All Rights Reserved 2

3 Part 2 Molecular Compounds Molecular compounds may be binary (containing two nonmetals held together by covalent bonds) or ternary (containing more than two different nonmetals). In naming binary molecular compounds, follow the rules below For binary molecular compounds that are NOT acids: The first atom is named first with its full name The second atom is named with its root plus an ide ending The number of atoms of each element are indicated by Greek prefixes The prefix mono is never used for the first atom For example, SF6 is sulfur hexafluoride and S2F10 is disulfur decafluoride Binary acids (compound with hydrogen) Follow the above rule, but do not use the prefix since hydrogen can only form one bond with any other atom For example, H2Se is hydrogen chloride Binary acids as a pure compound may be written Binary compounds with hydrogen become acids in their aqueous form The term (aq) is used to denote the acid is dissolved in water For example, HCl (aq) is hydrochloric acid But, HCl as a pure compound is hydrogen chloride To name ternary molecular compounds: Ternary acids (oxyacids) have a hydrogen and a polyatomic ion A per ate ion is named as a per ic acid HCLO4 (aq) has the perchlorate ion and is named perchloric acid An ate ion is named as an ic acid HCLO3 (aq) has the chlorate ion and is named chloric acid An ite ion is named as an ous acid HCLO2 (aq) has the chlorite ion and is named chlorous acid A hypo ite complex is named as a hypo ous acid HCLO (aq) has the hypochlorite ion and is named hypochlorous acid Experiment Molecular Compounds 1. Fill out the empty boxes in Table 2: Where there is a name, place the corresponding formula Where there is a formula, place the corresponding name. 2. Perform Data Analyses Part 2 3. Proceed to Part Catholic Initiatives in Math and Science, LLC All Rights Reserved 3

4 Part 3 Putting It All Together When confronted with a compound and asked to name it or to write the formula, you must first determine whether this is an ionic compound or a molecular compound. This is easily answered by determining whether the compound begins with a nonmetal or with ammonium ion. Once this question is answered, you can name the compound or write its formula by following a follow the flow of logical questions. If it is an Ionic Compound: 2016 Catholic Initiatives in Math and Science, LLC All Rights Reserved 4

5 If it is a Covalent Compound: Experiment Putting It All Together 1. Fill out the empty boxes in Table 3: Identify the compound as ionic or covalent Where there is a name, place the corresponding formula Where there is a formula, place the corresponding name. 2. Perform Data Analyses Part Catholic Initiatives in Math and Science, LLC All Rights Reserved 5

6 TABLE 1 Ionic Compounds FORMULA NAME SrI2 Lithium oxide CaCl2 NaCl Silver oxide FePO4 K2S Aluminum fluoride CuCl Copper(II) chloride FeCl2 Iron(III) chloride Mn3N4 Aluminum sulfide Data Analysis Part 1 1. What are the oxidation numbers for manganese and nitrogen in Mn3N4? 2. Give the name and formula for any ionic compound having a polyatomic ion Catholic Initiatives in Math and Science, LLC All Rights Reserved 6

7 TABLE 2 Molecular Compounds FORMULA NAME Xenon difluoride SO3 Diboron difluoride P4O10 H2Se Hydrogen chloride Hydroiodic acid HCl (aq) Sulfurous acid H2SO4 (aq) Nitrous acid HNO3 (aq) Hydrogen cyanide Data Analysis Part 2 3. Name the first ten Greek prefixes used in naming molecular compounds: # of Atoms Greek Prefix # of Atoms Greek Prefix 1 atom 6 atoms 2 atoms 7 atoms 3 atoms 8 atoms 4 atoms 9 atoms 5 atoms 10 atoms 2016 Catholic Initiatives in Math and Science, LLC All Rights Reserved 7

8 TABLE 3 Putting It All Together Ionic or Covalent? FORMULA NAME NI3 Sodium hydride BaI2 Sulfur hexafluoride CsBr Tin(II) iodide Co(C2H3O2)2 Potassium nitride Ag3PO4 Sulfur dioxide PO3 Ammonium nitrate CCl4 Iron(III) perchlorate N2O4 Data Analysis Part 3 Tetrasulfur tetranitride KCN 4. How do you determine whether a compound is molecular (covalent) or ionic? 2016 Catholic Initiatives in Math and Science, LLC All Rights Reserved 8