Covalent Nomenclature

Naming Molecular Compounds

Review How do we identify ionic formulas?

Ionic formulas start with metals (or NH4+1)

How do we identify covalent formulas? Covalent formulas contain only non-metals or metalloids.

How do we name ionic compounds? Identify the compound as binary or ternary. Identify the metal as fixed charge or variable charge. If the compound is binary, ends in –ide. If the compound is ternary, name the anion

appropriately.

Naming Molecular Compounds All the molecular compounds you’ll be asked to

name are binary. Molecular compounds w/ more than 2 elements are usually organic.

Organic compounds have their own special naming system.

Atoms in molecules don’t the number of each atom: mono = 1 di = 2 tri = 3 tetra = 4 penta = 5

hexa = 6 hepta = 7 octa = 8 nona = 9 deca = 10

Naming Molecular Compounds Prefix for first element in compound.

Omit if it’s “mono”. Name first element. Prefix for second element in compound. Give stem of second element followed by

suffix –ide. Examples:

CO = carbon monoxide CO2 = carbon dioxide N2O = dinitrogen monoxide

Details and Exceptions If the last letter of the prefix and the first

letter of the element are both vowels, drop the last letter of the prefix. CO = carbon monoxide, not carbon monooxide N2O5 = dinitrogen pentoxide, not dinitrogen

pentaoxide Some compounds are known only by their

common names H2O = water

NH3 = ammonia

CH4 = methane

Writing Formulas From Names Write symbols in the same order they

appear in the name. Use prefixes to determine subscripts. Metalloids are not metals.

Compounds that start with metalloids are named as molecular compounds.

Naming Molecular Compounds What are the names of the following

molecular compounds? NO2

SO3

SiO2

NO P2O5

S4N4

nitrogen dioxidesulfur trioxidesilicon dioxidenitrogen monoxidediphosphorus pentoxidetetrasulfur tetranitride

Writing Formulas From Names What are the formulas of the following

molecular compounds? carbon tetrachloride phosphorus trichloride selenium dibromide dinitrogen tetroxide sulfur dioxide xenon tetrafluoride diantimony trioxide

CCl4PCl3SeBr2

N2O4

SO2

XeF4

Sb2O3