Binary Covalent Compounds Composed of two nonmetals –can be same or different

Two naming systems Stock system: – learned for ionic compounds – “official” Traditional: – what hear on news – what see on ingredient lists

Both Traditional & Stock LeastLeast electronegative of two elements goes first REMINDER: – electronegativity values in table S

Stock System 1st element must have Roman Numeral Have to figure out oxidation number

Stock System & Oxidation Number N’Tmolecular substances DON’T contain ions use concept of oxidation number for electron bookkeeping –pretend all shared electrons go to atom with higher electronegativity value –oxidation number would be: atom with higher electronegativity value has (-) oxidation number atom with lower electronegativity value is (+)

7 Rules for Oxidation Numbers # for free, uncombined element = 0 Na He O 2 N 2 S 8 Cl 2 P # for monatomic ion = charge on ion2. Fluorine is always Ca +2 = +2 Cl -1 = -1 Al +3 = +3 CF 4 1.

Oxygen is nearly always -2 EXCEPT when its: Hydrogen is nearly always +1, except when bonded to a metal-then it’s LiH CaH 2 NaH OF 2 O Bonded to fluorine, where O is +2 -In the peroxide ion, where O is -1

The sum of oxidation numbers in a neutral compound is 0 The sum of oxidation numbers in a polyatomic ion = charge of the ion 6.7. H 2 O CO 2 NO SO 3 Sum in SO 4 2- = -2 Sum in NO 3 1- = -1

Naming Binary Covalent Compounds Stock System

CO 2 CO 2 : less C goes first: less electronegative than O CO 2 Each O is -2 Total = -4 Total = +4 so C is +4 so C is +4 Carbon (IV) oxide

Try SO 3 SO 3 Each O is -2 Total “neg” = -6 Total “pos” = +6 so S is +6 so S is +6 Sulfur (VI) Oxide

Try N 2 O 3 N2O3N2O3N2O3N2O3 Each O is -2 Total “neg” = -6 Total “pos” = +6 Each N is +3 Nitrogen (III) oxide

Try P 2 O 5 P2O5P2O5P2O5P2O5 Each O is -2 Total “neg” = -10 Total “pos” = +10 Each P is +5 Phosphorus (V) oxide

Naming Binary Covalent Compounds Traditional Naming System

Traditional Naming 1. less electronegative element named 1 st stem 2. stem 2 nd element plus “-ide” 3. prefixes tell how many of each element Exception: NEVER start a name with “mono-”

Prefixes: Traditional System deca10penta5 nona9tetra4 octa8tri3 hepta7di2 hexa6mono1 Prefix# of AtomsPrefix# of Atoms

Stems: just a reminder I = iodTe = tellur Br = brom Se = selen As = arsen Cl = chlorS = sulfP = phosph Si = silic F = fluorO = oxN = nitrC = carbH = hydr

Traditional Naming N2ON2O NO 2 NO N2H4N2H4 NH 3 H2OH2O dihydrogen monoxide nitrogen trihydride dinitrogen tetrahydride nitrogen monoxide nitrogen dioxide dinitrogen monoxide