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 Least 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 Numbers molecular 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 1. # for free, uncombined element = 0 Na He O2 N2 S8 Cl2 P 2. # for monatomic ion = charge on ion Ca+2 = +2 Cl-1 = -1 Al+3 = +3 3. Fluorine is always -1 CF4

a 4. Hydrogen is nearly always +1, except when bonded to a metal-then it’s -1 LiH CaH2 NaH 5. Oxygen is nearly always -2 EXCEPT when its: OF2 -Bonded to fluorine, where O is +2 O22- -In the peroxide ion, where O is -1

The sum of oxidation numbers in a neutral compound is 0 6. H2O CO2 NO SO3 The sum of oxidation numbers in a polyatomic ion = charge of the ion 7. Sum in SO42- = -2 Sum in NO31- = -1 8. For covalent molecules, pretend they are ionic (But doesn’t mean they have ions!!!)

Naming Binary Covalent Compounds Stock System

CO2 CO2 Each O is -2 so C is +4 Total = -4 Total = +4 C goes first: less electronegative than O Each O is -2 so C is +4 CO2 Total = -4 Total = +4 Carbon (IV) oxide

SO3 Try SO3 so S is +6 Each O is -2 Total “pos” = +6 Total “neg” = -6 Sulfur (VI) Oxide

N2O3 Try N2O3 Each N is +3 Each O is -2 Total “pos” = +6 Total “neg” = -6 Nitrogen (III) oxide

P2O5 Try P2O5 Each O is -2 Each P is +5 Total “pos” = +10 Total “neg” = -10 Phosphorus (V) oxide

Naming Binary Covalent Compounds Traditional Naming System

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

Prefixes: Traditional System deca 10 penta 5 nona 9 tetra 4 octa 8 tri 3 hepta 7 di 2 hexa 6 mono 1 Prefix # of Atoms

Stems: just a reminder I = iod Te = tellur Br = brom Se = selen As = arsen Cl = chlor S = sulf P = phosph Si = silic F = fluor O = ox N = nitr C = carb H = hydr

Traditional Naming dihydrogen monoxide nitrogen trihydride N2H4 NH3 H2O dihydrogen monoxide nitrogen trihydride dinitrogen tetrahydride nitrogen monoxide nitrogen dioxide dinitrogen monoxide