1. Writing a formula for an Ionic Compound:
1st Write the symbols for the ions side by side
(cation first):
2nd Cross over the charges :
Al+3 O-2
3rd Check the subscripts (the smallest
possible ratio of ions):
Al+3
O-2
Al2O3
Al2O3

2. Practice:
K+1 Br
Mg+2 Cl
Na+1 O
Mg+2 O
K+1 (NO3 )
Na+1 (SO4 )
Pb+2 (NO3 )
Al+3 (SO4 )
KBr
MgCl2
Na2O
Mg2O2
MgO
KNO3
Na2SO4
Pb (NO3)2
Al2(SO4)3

3. Writing names of ionic compounds:
Write the name of the cation followed
by the name of the anion:
cation
anion
Element’s name
Polyatomic
Monatomic
The suffix of the element name change by ide.
See reference table
(SO4 ) sulfate.
(NO3 ) nitrate.
Chlorine
Chloride
(NO2 ) nitrite.
Oxygen
Oxide

4. Examples:
MgCl2
Magnesium chloride
Na3PO4
Sodium phosphate
CaO
Calcium oxide
BaSO4
Barium sulfate

5. Writing names of ionic compounds:
If the cation has more than one
oxidation number, you must write it
between parenthesis (using roman
numeral):
Examples:
Fe2O3
Iron (III) oxide
CuCl
Copper (I) chloride

6. Practice:
Write the name of the following:
LiBr
Aluminum fluoride ---
MgO
Ba(OH)
Sodium carbonate
Cu(NO3)
Iron (III) chloride
NiSO
Sodium nitride
Lithium bromide
AlF3
Magnesium oxide
Barium hydroxide
Na2CO3
Copper (II) nitrate
FeCl3
Nickel (II) sulfate
Na3N

7. Binary Molecular Compounds:
Compounds made by two different nonmetals.
Examples:
CO2
HBr
P2O5

8. Naming Binary Molecular Compounds:
1)The first element in the formula is
always named first, using the entire
element name.
2) The second element in the formula is
named using the root of the element
& adding the suffix –ide.
3) Prefixes are used to indicate the
number of atoms of each type that
are present in the compound.

9. Prefixes # of atoms
Mono one
Di two
Tri three
Tetra four
Penta five
Hexa six
Hepta – seven
Octa eight
Nona nine
Deca ten

10. Naming Binary Molecular Compounds:
EXAMPLES:
N2O5 –
H2O --
N2O --
CO2 --
PCl5 --
SO3 --
NH3 --
dinitrogen pentoxide.
dihydrogen monoxide.
dinitrogen monoxide.
carbon dioxide.
phosphorus pentachloride.
sulfur trioxide.
nitrogen trihydride.

11. Writing Formulas (Molecular Compounds):
1) Write the element symbols in the same
order than it appears in the compound name.
2) Use subscripts to represent the number of
atoms of each element indicated by the
prefixes used.
Dinitrogen tetroxide
Dihydrogen monoxide
Diphosphorus monoxide ----
Carbon monoxide
Phosphorus trichloride -----
N2O4
H2O
P2O CO
PCl3

12. Practice:
1) CCl4----
2) Phosphorus tribromide –-
3) CO -----
4) Dichlorine pentoxide ----
5) HI(g) ---
6) Hydrogen chloride---
Carbon tetrachloride.
PBr3
Carbon monoxide.
Cl2O5
Hydrogen iodide.
HCl(g)

13. II - Write the formulas of the following:
Dinitrogen tetroxide
Dihydrogen monoxide
Diphosphorus monoxide ----
Carbon monoxide
Phosphorus trichloride -----
III - Write the names or the formulas for:
1) CCl4----
2) Phosphorus tribromide –-
3) CO -----
4) Dichlorine pentoxide ----
5) HI(g) ---
6) Hydrogen chloride---