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"H-O-H"?! WHAT'S THAT SPELL?!. WATER?. Nomenclature Chapter 5. Chemical Formulas. I. Binary Compounds – *there are two main classes of binary compounds A. Metal + Nonmetal B. Nonmetal + Nonmetal. Section 4.4 – Formulas of Compounds. A. A compound is:
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"H-O-H"?! WHAT'S THAT SPELL?! WATER? NomenclatureChapter 5
Chemical Formulas I. Binary Compounds – *there are two main classes of binary compounds A. Metal + Nonmetal B. Nonmetal + Nonmetal Section 4.4– Formulas of Compounds A. A compound is: *the word relative here refers to ratios The smallest piece of a compound that still has the identity and properties of the compound is known as a _______________________or _______________________. B. The identity of a compound can be expressed as a chemical formula. All chemical fomulas tell you:
C. Rules for Writing Formulas (p. 80) • Each atom present is represented by its element symbol. • 2. The number of each type of atom is indicated by a subscript written to the right of the element symbol. • 3. When only one atom of a given type is present, the subscript “1” is not written. • Examples: (Self Check Exercise 4.1 p. 80-81)
II. Naming Binary Ionic (metal + nonmetal) Compounds A. There are two types of binary ionic compounds 1. Type I – metal has fixed charge (representative elements plus Ag+, Zn2+ and Cd2+ ) Examples: 2. Type II – metal has a charge that may vary (transition, inner transition) Examples: B. Rules for Naming Type I Ionic Compounds 1. The cation (metal) is always named first and the anion is named second. 2. The name of the cation is just the name of that element. 3. The name of the anion takes the root name of the element with an “ide” ending. Examples –
Rules for Naming Type II Ionic Compounds • All of the same rules from above apply…with one addition: a roman numeral (I, II, III,…etc) is used to denote the charge on the metal. • *charge of metal can be figured out from reverse criss-cross method or just from the fact that net charge = 0 • Examples –
III. Naming Binary Covalent (nonmetal + nonmetal) Compounds • Rules • First element in formula is named first using the full element name. • The second element is named by using root element name plus “ide” ending. • Prefixes are used to denote the number of atoms present of each type. • 4. The prefix “mono” is never used on the first element in the formula. • Examples -
IV. Naming Compounds That Contain Polyatomic Ions A. Polyatomic ions are – 1. Special type: Oxyanions *see table 5.4 B. Rules for naming compounds with polyatomic anions. 1. Cation comes first, anion second. 2. Polyatomic ion names are not altered with “ide” endings or prefixes. 3. All other rules for naming type I and type II ionic compounds apply. Examples –
VI. Naming Acids An acid is – A. Binary Acids (H plus one other element) Rules 1. Binary acid names always start with the prefix “hydro” 2. After prefix use anion root name with “ic” ending. ` Examples – B. Acids Containing Polyatomic Ions Rules 1. NEVER use prefix “hydro” 2. anion may end in “ic” or “ous” (see page 131) Examples –
VII. Writing formulas from names. First, determine whether or not it is ionic, covalent, or an acid. 1. Ionic compounds and acids: Use criss-cross method (works for polyatomic ions too) *Examples – 2. Covalent Compounds: use prefixes as subscripts in formula. *Examples –
VIII. Molar Mass The mass (in grams) of 1 mole of the substance. Examples: Formula Weight-
IX. Percent Composition of Compounds Mass Fraction = _________________________________________ Mass Percent of something is the mass of something 1 mole of the compound. Examples:
X. Formulas of Compounds Empirical Formula- Examples: Molecular Formula- XI. Calculation of Empirical Formulas Steps: 1. Obtain the mass of each element present (in grams) 2. Determine the number of moles of each element. 3. Divide the number of moles of each element by the smallest number of moles of the elements present. 4. If needed, multiply the numbers from Step 3 by the smallest integer that will convert them to whole numbers. Best explained through examples
XII. Calculation of Molecular Formulas Can be calculated from % Compositions or from Empirical formulas You need 3 pieces of information: Empirical formula Empirical formula mass Molar Mass