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

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

4. Both Traditional & Stock
Least electronegative of two elements goes first
REMINDER:
electronegativity values in table S

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

6. 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. 7 Rules for Oxidation Numbers1.
# for free, uncombined element = 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
CF4

8. 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

9. 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- = Sum in NO31- = -1
8. For covalent molecules, pretend they are ionic (But doesn’t mean they have ions!!!)

10. Naming Binary Covalent Compounds
Stock System

11. 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

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

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

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

15. Naming Binary Covalent Compounds
Traditional Naming System

16. 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-”

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
# of Atoms

18. 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

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