1. Naming Covalent/ Molecular Compounds

2. Naming Covalent 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

3. 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 = deca

4. 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)

5. 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)

6. 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. Naming Covalent Compounds
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.

8. Naming Covalent Compounds (Continued)
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

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. Learning Check 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

11. Solution Select the correct name for each compound.
A. SiCl4 3) silicon tetrachloride
B. P2O5 3) diphosphorus pentoxide
C. Cl2O7 1) dichlorine heptoxide

12. Learning Check Write the correct formula for each of the following:
A. phosphorus pentachloride
B. dinitrogen trioxide
C. sulfur hexafluoride

13. Solution Write the correct formula for each of the following:
A. phosphorus pentachloride
1P penta = 5Cl PCl5
B. dinitrogen trioxide
di = 2N tri = 3 O N2O3
C. sulfur hexafluoride
1S hexa = 6F SF6

14. TRY THESE: Diphosphorus pentoxide Nitrogen monoxide Xenon hexafluoride
Tetrarsenic decoxide

15. More Examples
a) SiO2
b) N2S5
c)P4O10
d)BrCl6

16. Learning Check Write the name of each covalent compound.
PCl3 _____________________
CCl4 _____________________
N2O _____________________

17. Solution Write the name of each covalent compound. CO carbon monoxide
CO2 carbon dioxide
PCl3 phosphorus trichloride
CCl4 carbon tetrachloride
N2O dinitrogen oxide

18. Review of Covalent CompoundsHI
hydrogen iodide
NF3
nitrogen trifluoride
SO2
sulfur dioxide
N2Cl4
dinitrogen tetrachloride
NO2
nitrogen dioxide
N2O
dinitrogen monoxide

19. 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

20. 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

21. Learning Check Name the following compounds: A. Ca3(PO4)2 B. FeBr3
C. SCl2
D. Cl2O

22. Solution Name the following compounds:
A. Ca3(PO4)2 ionic Ca2+, PO43− calcium phosphate
B. FeBr3 ionic Fe3+, Br − iron(III) bromide
C. SCl covalent 1S, 2Cl sulfur dichloride
D. Cl2O covalent 2Cl, 1 O dichlorine oxide