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Naming Molecules Section 9.2
Chemistry
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Objectives Identify the names of binary molecular compounds from their formulas.
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Analogies The millions of compounds in the world and crayons in the Crayola® box
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Naming Binary Molecular Compounds
binary: a molecule that contains only two different elements. do not contain metals or ions Do contain two different nonmetals
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3 Rules for Naming Binary Compounds
The first element in the formula is always named first, using the entire element name. The second element in the formula is named using the root of the element and adding the suffix –ide.
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3 Rules for Naming Binary Compounds Cont.
Prefixes are used to indicate the number of atoms of each type that are present in the compound. Prefixes are similar to the ones used in geometry in naming polygons.
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Prefixes for Molecular Compounds
1 2 One – mono- Two – di- Three – tri- Four – tetra- Five – penta- 3 4 5
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Prefixes for Molecular Compounds Cont.
6 Six – hexa- Seven – hepta- Eight – octa- Nine – nona- Ten – deca- 7 8 9 10
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Prefixes for Molecular Compounds Cont.
One exception is that the first element in the formula never uses the prefix mono-. Ex: CO Incorrect: Monocarbon monooxide. Correct: Carbon monooxide.
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Example Problems Page 249 13-17
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Common Names of Compounds
Many binary compounds were discovered and given common names long before the modern naming system was developed. Examples: Page 249, table 9-2.
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Formulas and Names of Some Covalent Compounds
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Naming Acid Water solutions of some molecules are acidic and are named as acids If the compound produces hydrogen ions in solution, it is an acid.
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Naming Binary Acids A Binary Acid contains hydrogen and another element. When naming a binary acid , use the prefix hydro- to name the hydrogen part of the compound, The second element use the root name and the suffix -ic. Example: HBr
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Naming Oxyacids Any acid that contains hydrogen and an oxyanion is referred to as a oxyacid. Remember an oxyanion is a polyatomic ion that contains an oxygen atom
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Rules for Naming Oxyacids
Name depends on the oxyanion present The name of an oxyacid consists of a form of the root of the anion, a suffix , and the word acid If the oxyanion ends in –ate , it is replaced by –ic If the oxyanion ends in –ite, it is replaced by –ous
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Examples HNO3 HNO2
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Practice Problems Page 250
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Writing Formulas from Names
Subscripts are determined by prefixes Example: Dihydrogen monoxide
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Homework 23-29 on page 251
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