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Unit 7.1 Naming Molecular Compounds. Teacher: Dr. Van Der Sluys. Objectives. Naming molecular compounds Using prefixes Stock naming system. Prefixes. A prefix is a morpheme (portion of a word) that comes at the beginning of the word and has a specific meaning.
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Unit 7.1 Naming Molecular Compounds Teacher: Dr. Van Der Sluys
Objectives • Naming molecular compounds • Using prefixes • Stock naming system
Prefixes • A prefix is a morpheme (portion of a word) that comes at the beginning of the word and has a specific meaning
Naming Molecular Compounds with Prefixes • Use a prefix to indicate how many atoms there are of the first element in the formula, except if there is only one atom of the first element, then do not use the prefix mono-. • After the prefix, use the name of the first element in the formula. • Use a prefix to indicate the number of atoms for the second element in the formula. • Use the root of the second elements name and the suffix -ide.
Examples • N2O dinitrogen monoxide • NO nitrogen monoxide • NO2 nitrogen dioxide • CO2 carbon dioxide • CO carbon monoxide
More Examples • CF4 • SO2 • SF6 • Dichlorine heptaoxide • Hydrogen chloride • Phosphorus trichloride
Exceptions • H2O water • NH3 ammonia • Organic compounds - compounds containing carbon bonded to hydrogen have their own unique naming system • CH4 methane • C2H6 ethane • C3H8 propane
The Stock Naming System The International Union of Pure and Applied Chemists (IUPAC) have developed a naming system based on the oxidation numbers of the first element in the formula. • Name the first element. • Use a Roman numeral to indicate the oxidation number, by reversing the criss-cross and determining the charge as if it were an ionic compound. • Use the root of the second elements name and end with the suffix -ide.
Rationale • In compounds that contain polar covalent bonds, electrons are displaced towards the more electronegative atom. This results in partial positive negative charges. The stock naming system assumes that the bonding is ionic rather than covalent. .. .. .. .. O=C=O [:O:]2- [C]4+ [:O:]2- .. .. .. .. Carbon dioxide Carbon (IV) oxide
Example • CF4 C4+ and F- Carbon (IV) fluoride • N2O N+ and O2- Nitrogen (I) oxide • CO2 C4+ and O2- carbon (IV) oxide • SF6 S6+ and F- sulfur (VI) fluoride
Examples • CO • NO2 • Phosphorus (V) oxide • Chlorine (VII) oxide
Summary • Prefixes are used to indicate the number of each element in the formula • Stock naming system uses roman numerals to indicate the charge of the first element as determine from the criss-cross system.