Naming Covalent/ Molecular Compounds
Hydrogen compounds are handled differently and will be looked at first.
Nomenclature:1) Name the hydrogen that appears in the formula.
2) Name the second element that appears in the formula, changing its ending to –ide. (Similar to ionic compounds)
Examples:HCl hydrogen chloride
HI hydrogen iodide
Naming Covalent CompoundsNaming Covalent Compounds
Covalent Bonds use prefixes to indicate the number of atoms involved in the compounds
1= mono 6 = hexa
2 = di 7= hepta
3 = tri 8 = octa
4 = tetra 9 = nona
5 = penta 10 = deca
RULES
1- The name of the first element does not get changed, only a prefix is added if it is more than one.
Ex: Trisulfur tetrafluoride S3F4
2- The second element gets a different ending, as well as a prefix.
Ex : phosphorus trichloride PCl3(NOT: phosphorus trichlorine)
RULES continued..
3- If the first element in the compound is single you do not write mono:
ex. CO2 - carbon dioxide (NOT monocarbon dioxide)
4- If the element’s name starts with a vowel, and the prefix ends with a vowel, you can drop the last vowel on the prefix:
ex. S5O10 - pentasulfur decoxide(NOT pentasulfur decaoxide)
RULES continued..
5- Covalent compounds do not get simplified. Name the compound exactly as you see it:
Ex. H2F2 = dihydrogen difluoride
(NOT hydrogen monofluoride HF)
7
What is the name of SO3?
STEP 1 The first nonmetal is S sulfur.
STEP 2 The second nonmetal is O, named oxide.
STEP 3 The subscript 3 of O is shown as the prefix tri.
SO3 → sulfur trioxide
The subscript 1(for S) or mono is understood.
Naming Covalent Compounds
8
Name P4S3
STEP 1 The first nonmetal P is phosphorus.
STEP 2 The second nonmetal S is sulfide.
STEP 3 The subscript 4 of P is shown as tetra.
The subscript 3 of O is shown as tri.
P4S3 → tetraphosphorus trisulfide
Naming Covalent Compounds (Continued)
9
Names of Covalent Compounds
Remember Prefixes are used in the names of covalent compounds because two nonmetals can form two or more
different compounds
Examples of compounds of N and O:
NO nitrogen oxide
NO2 nitrogen dioxide
N2O dinitrogen oxide
N2O4 dinitrogen tetroxide
N2O5 dinitrogen pentoxide
10
Select the correct name for each compound.
A. SiCl4 1) silicon chloride
2) tetrasilicon chloride
3) silicon tetrachloride
B. P2O5 1) phosphorus oxide
2) phosphorus pentoxide
3) diphosphorus pentoxide
C. Cl2O7 1) dichlorine heptoxide
2) dichlorine oxide
3) chlorine heptoxide
Learning Check
11
Select the correct name for each compound.
A. SiCl4 3) silicon tetrachloride
B. P2O5 3) diphosphorus pentoxide
C. Cl2O7 1) dichlorine heptoxide
Solution
12
Write the correct formula for each of the following:
A. phosphorus pentachloride
B. dinitrogen trioxide
C. sulfur hexafluoride
Learning Check
13
Write the correct formula for each of the following:
A. phosphorus pentachloride
1P penta = 5Cl PCl5B. dinitrogen trioxide
di = 2N tri = 3 O N2O3
C. sulfur hexafluoride
1S hexa = 6F SF6
Solution
TRY THESE:
a) Diphosphorus pentoxide
b) Nitrogen monoxide
c) Xenon hexafluoride
d) Tetrarsenic decoxide
a) SiO2
b) N2S5
c)P4O10
d)BrCl6
More Examples
16
Formulas, Names and Uses of Some Covalent Compounds
17
Write the name of each covalent compound.
CO _____________________
CO2 _____________________
PCl3 _____________________
CCl4 _____________________
N2O _____________________
Learning Check
18
Write the name of each covalent compound.
CO carbon monoxide
CO2 carbon dioxide
PCl3 phosphorus trichloride
CCl4 carbon tetrachloride
N2O dinitrogen oxide
Solution
HI hydrogen iodide
NF3 nitrogen trifluoride
SO2 sulfur dioxide
N2Cl4 dinitrogen tetrachloride
NO2 nitrogen dioxide
N2O dinitrogen monoxide
Review of Covalent Compounds
20
Ionic and Covalent
Identify each compound as ionic or covalent, and give its correct name.
A. SO2
B. BaCl2
C. (NH4)3PO4
D. Cu2CO3
E. N2O4
21
Solution
Identify each compound as ionic or covalent, and give its correct name.
A. SO2 covalent; sulfur dioxide
B. BaCl2 ionic; barium chloride
C. (NH4)3PO4 ionic; ammonium phosphate
D. Cu2CO3 ionic; copper(I) carbonate
E. N2O4 covalent; dinitrogen tetroxide
22
Learning Check
Name the following compounds:
A. Ca3(PO4)2
B. FeBr3
C. SCl2D. Cl2O
23
Solution
Name the following compounds:
A. Ca3(PO4)2 ionic Ca2+, PO43− calcium
phosphate
B. FeBr3 ionic Fe3+, Br − iron(III) bromide
C. SCl2 covalent 1S, 2Cl sulfur dichloride
D. Cl2O covalent 2Cl, 1 O dichlorine oxide
Homework
Page 249Problems: 14, 15, 16 and 17
Page 274Problems: 93, 94 and 95 (a-c)