8 - 1 Covalent Nomenclature  Covalent (molecular) compounds have both an empirical and a molecular formula.  An empirical formula is a formula showing the simplest ratio in which the atoms the simplest ratio in which the atoms combine to form a compound. combine to form a compound.   A molecular formula indicates the number of atoms of each element in one molecule of a substance.

Some Some Common Compounds CompoundEmpirical Formula Molecular Formula water H 2 O ammonia NH 3 hydrogen peroxide HO H 2 O 2 methane CH 4 acetylene CH C 2 H 2

8 - 3 Traditional System.  Prefixes are used with both the 1 st named and 2 nd named elements.  Never use mono- with the first named element! MM with Junebug or Sophia.

8 - 4 Prefixes Used With Traditional System. Number of Atoms PrefixNumber of Atoms Prefix 1 mono-6 hexa- 2 di-7 hepta- 3 tri-8 octa- 4 tetra-9 nona- 5 penta- 10 deca-

8 - 5 Traditional Nomenclature. Chemical FormulaName PF 3 phosphorus trifluoride CCl 4 carbon tetrachloride PCl 5 phosphorus pentachloride N 2 Odinitrogen monoxide NO 2 nitrogen dioxide NOnitrogen monoxide

8 - 6 Traditional Nomenclature. NameChemical Formula phosphorus trifluoride PF 3 carbon tetrachloride CCl 4 phosphorus pentachloride PCl 5 dinitrogen monoxide N 2 O nitrogen dioxide NO 2 nitrogen monoxide NO

8 - 7 Stock System  Stock system never uses prefixes.  Stock system uses a roman numeral in parenthesis to indicate the apparent charge on the atom with a positive oxidation number.  Never mix and match the traditional and the stock system!

8 - 8 Stock System Nomenclature. Chemical Formula Name PF 3 phosphorus(III) fluoride CCl 4 carbon(IV) chloride PCl 5 phosphorus(V) chloride N 2 Onitrogen(I) oxide NO 2 nitrogen(IV) oxide NOnitrogen(II) oxide

8 - 9 Stock System Nomenclature. Name Chemical Formula phosphorus(III) fluoride PF 3 carbon(IV) chloride CCl 4 phosphorus(V) chloride PCl 5 nitrogen(I) oxide N 2 O nitrogen(IV) oxide NO 2 nitrogen(II) oxide NO