Binary Covalent Compounds Composed of two nonmetals can

Binary Covalent Compounds • Composed of two non-metals –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 • See table S

Stock System 1 st element must have Roman Numeral so… figure out oxidation number

Stock System & Oxidation Number • molecular substances DON’T contain ions • concept of oxidation # for e- bookkeeping – pretend all shared e- go to atom with higher electronegativity value • atom with higher electronegativity value: (-) oxidation # • atom with lower electronegativity value: (+) oxidation #

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

4. Hydrogen is nearly always (+)1, except when bonded to metal, then (-)1 Li. H Ca. H 2 Na. H 5. Oxygen is nearly always (-)2 EXCEPT when: -Bonded to fluorine: O is (+)2 -In peroxide ion: O is (-)1 OF 2 O 22 -

6. sum oxidation numbers in neutral compound is 0 H 2 O CO 2 NO SO 3 7. sum of oxidation numbers in polyatomic ion = charge of ion Sum in SO 42 - = -2 Sum in NO 31 - = -1

Naming Binary Covalent Compounds Stock System

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

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

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

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

Naming Binary Covalent Compounds Traditional Naming System

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

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

Traditional Naming H 2 O dihydrogen monoxide NH 3 nitrogen trihydride N 2 H 4 dinitrogen tetrahydride NO nitrogen monoxide NO 2 nitrogen dioxide N 2 O dinitrogen monoxide