Topic: Naming Binary Covalent Compounds

Do Now: 1)

2)

3)

4)

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

a

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

# for free, uncombined element = 0

Na He O2 N2 S8 Cl2 P

# for monatomic ion = charge on ion2.

Fluorine is always -13.

Ca+2 = +2 Cl-1 = -1 Al+3 = +3

CF4

1.

CF4

-1+4

Oxygen is nearly always -2 EXCEPT when its:

Hydrogen is nearly always +1, except when bonded to a metal-then it’s -1

4.

5.

HCl LiH CaH2

OF2-Bonded to fluorine, where O is +2

-In the peroxide ion, where O is -1

+1 -1 -1 -1+1 +2

+2 -1

H2O2

+1 -1

The sum of oxidation numbers in a neutral compound is 0

6.

H2O CO2 NO+1 -2

+1 (2) + -2(1) = 0

+4 -2

+4 (1) + -2(2) = 0

+2 -2

+2 (1) + -2(1) = 0

The sum of oxidation numbers in a polyatomic ion = charge of the ion

7.

Sum in SO42- = -2 Sum in NO3

1- = -1

For covalent molecules, pretend they are ionic (But doesn’t mean they have ions!!!)

+6 -2

+6 (1) + -2(4) = -2

+5 -2

+5 (1) + -2(3) = -2

Naming Binary Covalent Compounds

Stock System

CO2

CO2: C goes first: less electronegative than O

CO2

Each O is -2

Total = -4Total = +4

so C is +4

Carbon (IV) oxide

Try SO3

SO3

Each O is -2

Total “neg” = -6Total “pos” = +6

so S is +6

Sulfur (VI) Oxide

Try N2O3

N2O3

Each O is -2

Total “neg” = -6Total “pos” = +6

Each N is +3

Nitrogen (III) oxide

Try P2O5

P2O5

Each O is -2

Total “neg” = -10Total “pos” = +10

Each P is +5

Phosphorus (V) oxide

Naming Binary Covalent Compounds

Traditional Naming System

Traditional Naming

1. less electronegative element named 1st

2. stem 2nd 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 = selenAs = arsen

Cl = chlorS = sulfP = phosph

Si = silic

F = fluorO = oxN = nitrC = carbH = hydr

Traditional Naming

N2O

NO2

NO

N2H4

NH3

H2O dihydrogen monoxide

nitrogen trihydride

dinitrogen tetrahydride

nitrogen monoxide

nitrogen dioxide

dinitrogen monoxide