WRITING FORMULAS AND
NAMING COMPOUNDS
Binary Compounds
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Made up of only 2 elements
Two types of Binary Compounds
1. Ionic Compounds- metal and nonmetal
Ex: NaCl, MgBr2, K2O
2. Covalent Compounds- 2 nonmetals
Ex: CO2, H2O, SO3
Ionic or Covalent?
1. NO2
covalent
2. P2O4
covalent
3. Fe2O3
ionic
4. CaF2
ionic
Covalent Compounds
NAMING
A. Use prefixes to indicate the number of atoms of
each element
mono-1
hexa-6
di-2
hepta-7
tri-3
octa-8
tetra-4
nona-9
penta-5
deca-10
B. Name the first element. If you have only one atom
of the first element, do NOT use the prefix mono.
C. Name the second element with prefixes. Change
the ending to “ide”.
Name the following:
1. CO2
carbon dioxide
2. SO3
sulfur trioxide
3. N2O4
dinitrogen tetroxide
4. CCl4
carbon tetrachloride
5. H2O
dihydrogen monoxide
Write the formula
1. phosphorus trichloride
PCl3
2. nitrogen dioxide
NO2
3. sulfur hexabromide
SBr6
4. diphosphorus pentoxide
P2O5
Ionic Compounds
NAMING
A. Name the first element (metal)
B. Name the second element (nonmetal) and change
the ending to “ide”
C. NO PREFIXES!!!
Name the following:
1. NaCl
sodium chloride
2. CaF2
calcium fluoride
3. Ag2O
silver oxide
4. AlBr3
aluminum bromide
5. ZnS
zinc sulfide
Writing Formulas
Ionic compounds are composed of a positive ion
called a cation and a negative ion called an anion.
A. Write the metal ion first. (+ ion: cation)
B. Write the nonmetal last. (- ion: anion)
C. Balance the charges! Charges must add up to zero
to form a neutral compound.
How to determine the charge
You can look at the position of the element on the
periodic table to determine the charge of the
element when it forms an ion.
There is a difference between a neutral element (K)
and an ion (K+).
Using the Periodic Table
Writing Formulas
1. sodium chloride
Na+ ClNaCl
2. calcium chloride
Ca+2 ClClCaCl2
Writing Formulas
3. aluminum chloride
Al+3
ClClClAlCl3
Writing Formulas
4. potassium bromide
K+ BrKBr
5. potassium oxide
K+ O-2
K+
K 2O
Writing Formulas
6. aluminum oxide
Al+3 O-2
Al+3 O-2
O-2
Al2O3
Review
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Covalent compounds are made up of nonmetals
only.
Use prefixes in the names of covalent compounds.
Covalent compounds do not have charges!
Ionic compounds are made up of a metal and a
nonmetal.
Balance the charges when you write a formula for
ionic compounds.
Never use prefixes in the names of ionic compounds!
Ionic Compounds with Roman Numerals
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The roman numeral gives the charge of the metal
ion.
Ex: Fe(II) Fe+2
Fe(III) Fe+3
Transition metals need roman numerals in the name.
Pb and Sn need roman numerals because they have
charges of +2 and +4.
Ag and Zn do NOT need roman numerals because
Ag is always +1 and Zn is always +2.
Write the Formula
1. nickel (II) bromide
NiBr2
2. lead (IV) oxide
PbO2
3. iron (III) sulfide
Fe2S3
Name the following
1. CrCl3
chromium (III) chloride
2. FeO
iron (II) oxide
3. SnCl4
tin (IV) chloride
4. Cu2O
copper (I) oxide
Review: Write the Formula
1.
2.
3.
4.
5.
strontium fluoride
chromium (III) oxide
sulfur hexabromide
iron (III) sulfide
carbon disulfide
1.
2.
3.
4.
5.
SrF2
Cr2O3
SBr6
Fe2S3
CS2
Review: Name the following.
1.
2.
3.
4.
5.
K2Se
CaI2
NiCl2
PCl3
BaNa2
1.
2.
3.
4.
5.
potassium selenide
calcium iodide
nickel (II) chloride
phosphorus
trichloride
banana 
Compounds with Polyatomic Ions
Naming
 Name the metal
 Name the polyatomic ion
 Use roman numeral if needed
Naming
1. MgCO3
magnesium carbonate
2. Na2SO4
sodium sulfate
3. Cu(OH)2
copper (II) hydroxide
4. Zn(C2H3O2)2
zinc acetate
Write the Formula:
1. aluminum nitrate
Al(NO3)3
2. ammonium sulfite
(NH4)2SO3
3. iron (III) chlorate
Fe(ClO3)3
4. calcium phosphate
Ca3(PO4)2