Writing Formulas for Binary Ionic
Compounds
• Binary Compounds:
– Compounds composed of 2 elements.
• When writing names, the positive charge, the
cation, must balance the negative charge of
the anion.
– Example: potassium chloride
• K+ Cl• KCl
Naming Binary Ionic Compounds
• When naming binary compounds with metals
that are not transition, just name metal and
nonmetal.
– Example:
• CaCl2
–Calcium chloride
• Li3N
–Lithium nitride
Binary Compounds, continued
• More examples:
– Calcium Bromide
• Ca2+ Br1• CaBr2
– Iron (III) Oxide
• Fe3+ O2• Fe2O3
– Calcium Sulfide
• Ca2+ S2• Ca2S2
• CaS
Naming Binary Ionic Compounds With
Transition Metals
• CuO
• Is it copper (I) or copper (II)?
• Work Backwards:
– 1. What is the charge of oxygen?
• 2– 2. How many oxygen atoms are there?
•1
– 3. So your overall negative charge is what?
• 2- (2- x 1)
Naming Binary Ionic Compounds,
continued
– 4. What charge must balance out a
negative 2?
• Positive 2
– 5. How many atoms of copper are there?
•1
– 6. So what is the charge of the copper
atom?
• 2+ (2+ ÷ 1)
Ternary Ionic Compounds
• Ternary Ionic Compounds:
– A compound that contains atoms of three
different elements.
• How would you write the formula for calcium
nitrate?
– 1. Write the symbol(s) and charge for each
part of the word.
• Ca2+ NO31-
Ternary Ionic Compounds, continued
– 2. Then cross and drop to balance your
charges. (*If you need to cross and drop a
number other than one next to a polyatomic
ion, use parenthesis.)
• Ca(NO3)2
– Write the symbol(s) and charge for each part
of the word.
• Mg2+ PO43• Mg3(PO4)2
Molecules
Molecules:
Smallest electrically neutral unit of a substance
that still has the properties of the substance.
Made of 2 or more nonmetals that act as a unit.
Diatomics:
2 atoms
I2, Br2, Cl2, F2, O2, N2, H2
Triatomics:
3 atoms
H2O, CO2, O3
Naming Binary Molecular Compounds
• Use the prefixes in Table 6.5. MEMORIZE THESE!!!
–
–
–
–
–
–
–
–
–
–
Mono- means 1
Di- means 2
Tri- means 3
Tetra- means 4
Penta- means 5
Hexa- means 6
Hepta- means 7
Octa- means 8
Nona- means 9
Deca- means 10
Naming Binary Molecular Compounds,
continued
• *The only time you use the prefix mono- is when you have
one of the second element. You NEVER use mono- on the first
element.
• CO2
– Carbon dioxide
• CO
– Carbon monoxide
• PCl3
– Phosphorous trichloride
• Cl2O8
– Dichlorine octoxide
Naming Acids
• If Hydrogen is the first element in your
compound, you have an acid.
• If it is a binary acid, 2 elements, use the prefix
hydro- put the root word and then end in –ic.
– Example: HCl
• Hydrochloric
– Example: H3N
• Hydronitric
Naming Acids, cont.
• If you have more than 2 elements, you have a
polyatomic present in your acid.
– All you change is the ending.
• If the polyatomic normally ends in –ate, change the
ending to –ic.
• If the polyatomic normally ends in –ite, change the
ending to –ous.
Naming Acids, cont.
• Example:
– HNO3
• H is present, so we know it’s an acid.
• NO3 is nitrate
• So, we have nitric acid
– HC2H3O2
• H is present, so we know it’s an acid.
• C2H3O2 is acetate
• So, we have acetic acid
Naming Acids, continued
• Example:
– HNO2
• H is present so we know we have an acid.
• NO2 is nitrite
• So we have nitrous acid
– H3PO3
• H is present so we know we have an acid.
• PO3 is phosphite
• So we have phosphorous acid
The Flow Chart
Is the first element
in your compound
an H?
No
Are there more than
2 elements?
Yes
Yes
No
Is the metal a
transition metal?
Yes
Yes
Do you have both a
metal and a nonmetal
present?
No
Find the charge
of the metal working
backwards. Use roman
numerals to identify the
charge. Then
name the nonmetal with
-ide at the end.
No
Name the metal
as normal, then name
the nonmetal using
-ide on the end.
You have an acid.
Name it appropriately.
You have a polyatomic
present. What is it?
Once you’ve found that
name as normal.
If you have a metal that
is a transition metal, use
roman numerals. If not just
name it as normal.
It is a molecular
compound. Use prefixes
to name it.