2. Binary Covalent Compounds
Composed of two non-metals
can be same or different

3. Two naming systems stock system: system learned for ionic compounds
uses roman #
traditional:
hear on news, see on ingredient lists
sytem for naming molecules
uses prefixes

4. Both Naming Systems
least electronegative of non-metal elements written first
see table S

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

6. Oxidation Number
molecular substances DON’T contain ions so use 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. 7 Rules for Oxidation Numbers1.
# for free, uncombined element is 0
Na He O2 N2 S8 Cl2 P 2.
# for monatomic ion = charge on ion
Ca+2 = Cl-1 = Al+3 = +3 3.
fluorine is always (-)1
+4 -1
CF4

8. 4.
Hydrogen is nearly always (+)1, except when bonded to metal, then (-)1
LiH CaH2 NaH

9. Oxygen is nearly always (-)2 EXCEPT when:5.
Oxygen is nearly always (-)2 EXCEPT when:
OF2
-bonded to fluorine: O is (+)2
O22-
-in peroxide ion: O is (-)1
(only with group 1 or 2 metals)
MgO2

10. sum oxidation numbers in neutral compound is 06.
sum oxidation numbers in neutral compound is 0
H2O CO2 NO SO3 7.
sum of oxidation numbers in polyatomic
ion = charge of ion
Sum in SO42- = Sum in NO31- = -1

11. Naming Binary Covalent Compounds
Stock System

12. 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

13. SO3 Try SO3 so S is +6 Each O is -2 Total “pos” = +6 Total “neg” = -6
sulfur (VI) oxide

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

15. Naming Binary Covalent Compounds
Traditional Naming System

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

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

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