Molecular Compounds Writing Names and Formulas

Molecular Compounds l Molecular compounds are made of molecules. l They are made by joining nonmetal atoms together into molecules.

Naming is Easier l A molecular compound’s name tells you the number of atoms through the use of prefixes.

Prefixes l 1 mono- l 2 di- l 3 tri- l 4 tetra- l 5 penta- l 6 hexa- l 7 hepta- l 8 octa- l 9 nona- l 10 deca-

Prefixes l The name will consist of two words. Prefixnameprefixname-ide l One exception is we don’t write mono- if there is only one of the first element.

Prefixes l The following double vowels cannot be used when writing names:  (oa)  (oo)

Example l NO 2 l There is one nitrogen  mononitrogen l But, you cannot use mono- on the first element, so drop the prefix.  mononitrogen  nitrogen

Example l NO 2 l There are two oxygens  dioxygen

Example l NO 2  dioxygen l You need the suffix -ide  dioxygenide

Example l NO 2  nitrogen dioxide

Example lN2OlN2O l There are two nitrogens  dinitrogen l There is one oxygen  monooxygen

Example lN2OlN2O  monooxygen l You cannot run (oo) together, so  monoxygen

Example lN2OlN2O  monoxygen l You need the suffix -ide  monoxygenide

Example lN2OlN2O  dinitrogen monoxide

Problem l Name the following molecular compounds.  Cl 2 O 7  CBr 4 dichlorine heptoxide carbon tetrabromide

Problem l Name the following molecular compounds.  CO 2  BCl 3 carbon dioxide boron trichloride

Naming Molecular Compounds l You will not need to criss-cross oxidation numbers. l Molecular compounds name tells you the number of atoms through the use of prefixes.

Example l diphosphorus pentoxide l The name implies there are 2 phosphorous atoms and 5 oxygens. P2O5P2O5

Example l sulfur hexaflouride l The name implies there is 1 sulfur atom and 6 fluorines. SF 6

Problem l Write the formulas for the following molecules.  tetraiodide nonoxide  nitrogen trioxide I4O9I4O9 NO3NO3

Problem l Write the formulas for the following molecules.  carbon tetrahydride  phosphorus trifluoride CH 4 PF3PF3