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Unformatted text preview: CHM151LL: CHEMICAL NOMENCLATURE | 1 Chemical Nomenclature OBJECTIVES: Develop the skills needed to: write chemical formulas from names write names from formulas balance chemical equations DISCUSSION: In chemistry lab and lecture classes this semester you will need to recognize hundreds of compounds by formula and name. You will find it much more efficient to learn some general rules than to memorize all those substances. This lab discussion and the exercises that follow will help you develop the necessary skills in naming, formula writing and equation balancing that you will need for this and subsequent general chemistry classes. Nomenclature The nomenclature rules in chemistry serve the role of grammar and spelling rules in language. Sometimes they may seem confusing, and exceptions do exist, but the rules make it possible to recognize thousands of compounds without memorizing all the formulas and names. The International Union of Pure and Applied Chemistry (IUPAC) governs nomenclature for all branches of chemistry worldwide. The naming systems discussed in this brief review conform to the IUPAC Commission on the Nomenclature of Inorganic Chemistry Recommendations 1990. For some common compounds, like water (H 2 O) and ammonia (NH 3 ), we dont follow the IUPAC rules. Instead of systematic IUPAC names, these compounds go by their long- established "trivial" names. Organic chemistry and biochemistry have their own well-developed systems of nomenclature, which you will learn when you need them in later courses. Compound Classification Most of the compounds encountered in general chemistry fall into one of these general categories: 1. BINARY IONIC: metal with nonmetal 2. BINARY COVALENT: both nonmetals 3. BINARY ACID: hydrogen with nonmetal, in aqueous solution 4. TERNARY IONIC: metal or ammonium with polyatomic anion 5. TERNARY ACID: hydrogen with polyatomic anion, in aqueous solution To categorize a compound, first classify it as binary or ternary . Binary compounds have exactly two elements, ternary compounds have more than two . Once you have assigned the compound to the proper group, then you can further classify it. Table 1 illustrates the scheme and gives some examples. Table 1: Classification scheme for inorganic compounds. INORGANIC COMPOUNDS BINARY TERNARY IONIC COVALENT ACIDS IONIC ACIDS NaI, PbBr 2 CCl 4 , HCl ( g ) HCl ( aq ) K 2 CO 3 , (NH 4 ) 3 PO 4 H 2 SO 3 ( aq ), H 3 PO 4 ( aq ) 2 | CHM151LL: CHEMICAL NOMENCLATURE Prior Knowledge In order to write correct chemical formulas or names you must already have learned: the names and symbols for the elements, the ionic charges of the elements which have only one ionic charge, which elements have more than one ionic charge, and the names, formulas and ionic charges of the polyatomic ions from Table 2....
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- Spring '12