1. Molecules and Ions
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2. Molecules
Two or more atoms of the same or different elements, covalently bonded together.
Molecules are discrete structures, and their formulas represent each atom present in the molecule.
Pentane, C5H12

3. Covalent Network Substances
Covalent network substances have covalently bonded atoms, but do not have discrete formulas.
Why Not??
Graphene – carbon allotrope

4. Ions Cation: A positive ion Mg2+, NH4+ Anion: A negative ion
Cl−, SO42−
Ionic Bonding: Force of attraction between oppositely charged ions.
Ionic compounds form crystals, so their formulas are written empirically (lowest whole number ratio of ions).

5. Predicting Ionic Charges
Group 1: Lose 1 electron to form 1+ ions H+
Li+
Na+ K+
Rb+
Cs+

6. Predicting Ionic Charges
Group 2: Loses 2 electrons to form 2+ ions
Be2+
Mg2+
Ca2+
Sr2+
Ba2+

7. Predicting Ionic Charges
Group 13: Loses 3
electrons to form
3+ ions
B3+
Al3+
Ga3+

8. Predicting Ionic Charges
Loses 4
electrons or gains
4 electrons
Group 14:
Caution! C22- and C4- are both called carbide

9. Predicting Ionic Charges
Nitride
Gains 3
electrons to form
3- ions
Group 15:
Phosphide
P3-
As3-
Arsenide

10. Predicting Ionic Charges
Oxide
Group 16: Gains 2
electrons to form
2- ions
S2-
Sulfide
Se2-
Selenide

11. Predicting Ionic Charges
Group 17: Gains 1
electron to form
1- ions
F1-
Fluoride
Cl1-
Chloride
Br1-
Bromide
I1-
Iodide

12. Predicting Ionic Charges
Group 18: Stable Noble gases do not form ions!

13. Predicting Ionic Charges
Groups : Many transition metals have more than one possible oxidation state.
Iron(II) = Fe2+
Iron(III) = Fe3+

14. Predicting Ionic Charges
Groups : Some transition metals
have only one possible oxidation state.
Zinc = Zn2+
Silver = Ag+

15. Writing Ionic Compound Formulas
Example: Barium nitrate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Ba2+
( )
NO3- 2
Not balanced

16. Writing Ionic Compound Formulas
Example: Ammonium sulfate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
( )
NH4+
SO42- 2
Not balanced

17. Writing Ionic Compound Formulas
Example: Iron(III) chloride
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Fe3+
Cl- 3
Not balanced

18. Writing Ionic Compound Formulas
Example: Aluminum sulfide
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Al3+
S2- 2 3
Not balanced

19. Writing Ionic Compound Formulas
Example: Magnesium carbonate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
Mg2+
CO32-
They are balanced

20. Writing Ionic Compound Formulas
Example: Zinc hydroxide
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
( )
Zn2+
OH- 2
Not balanced

21. Writing Ionic Compound Formulas
Example: Aluminum phosphate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
Al3+
PO43-
They ARE balanced

22. Naming Ionic Compounds
Cation first, then anion
Monatomic cation = name of the element
Ca2+ = calcium ion
Monatomic anion = root + -ide
Cl− = chloride
CaCl2 = calcium chloride

23. Naming Ionic Compounds
Metals with multiple oxidation states
some metal forms more than one cation
use Roman numeral in name
PbCl2
Pb2+ is cation
PbCl2 = lead(II) chloride

24. Binary Molecular Compounds
Compounds between two nonmetals
First element in the formula is named first.
Keeps its element name
Gets a prefix if there is a subscript on it
Second element is named second
Use the root of the element name plus the -ide suffix
Always use a prefix on the second element

25. List of Prefixes 1 = mon(o) 2 = di 3 = tri 4 = tetra 5 = penta
6 = hexa
7 = hepta
8 = octa
9 = nona
10 = deka
List of Prefixes

26. Naming Binary Compounds
diphosphorus pentoxide
CO2 =
carbon dioxide
CO =
carbon monoxide
N2O =
dinitrogen monoxide

27. Practice – Write the Formula
Compound Name
Compound Formula
Carbon dioxide
Carbon monoxide
Diphosphorus pentoxide
Dinitrogen monoxide
Silicon dioxide
Carbon tetrabromide
Sulfur dioxide
Phosphorus pentabromide
Iodine trichloride
Nitrogen triiodide
Dinitrogen trioxide
Check next slide for answers

28. Answers – Write the Formula
Compound Name
Compound Formula
Carbon dioxide
CO2
Carbon monoxide CO
Diphosphorus pentoxide
P2O5
Dinitrogen monoxide
N2O
Silicon dioxide
SiO2
Carbon tetrabromide
CBr4
Sulfur dioxide
SO2
Phosphorus pentabromide
PBr5
Iodine trichloride
ICl3
Nitrogen triiodide
NI3
Dinitrogen trioxide
N2O3

29. Practice – Name the Compounds
Compound Formula
Compound Name
N2O4
SO3 NO
NO2
As2O5
PCl3
CCl4
H2O
SeF6
Check next slide for answers

30. Answers – Name the Compounds
Compound Formula
Compound Name
N2O4
dinitrogen tetroxide
SO3
sulfur trioxide NO
nitrogen monoxide
NO2
nitrogen dioxide
As2O5
diarsenic pentoxide
PCl3
phosphorus trichloride
CCl4
carbon tetrachloride
H2O
dinitrogen monoxide
SeF6
selenium hexafluoride