How do you know which type of compound it is?
Metal + Non-metal
(cation and anion; transfer of electrons)
Instructions
for:
Writing
Formulas
(also known
as
compounds)
3 or more elements
(cation and anion;
transfer of electrons)
Compounds
beginning with
Hydrogen
Ionic
Covalent
Polyatomic Ionic (and Bases)
Acids
1. Look up the oxidation numbers (number of electrons to
be given or taken) for each ion.
**If the metal is a transition metal, use the roman numeral
given as the oxidation number.
2. Criss-cross the charges to form subscripts (non-charged
numbers at the bottom) after each element in the formula.
Use the prefix given to indicate
the subscript after each element
in the compound.
1. Look up the oxidation numbers for any ions
on the periodic table or on the polyatomic ion
list.
2. Criss-cross the charges to form subscripts
after each element or molecule in the formula.
1. If the word acid
is found in the
name, you know
that the cation
(first element of
compound) will
be hydrogen.
2. To find the
anion, look at the
prefix/suffix on
the stem, and the
rules for each.
3. Criss-cross
charges.
Example 1:
magnesium phosphide
Step 1) Mg2+ P3Step 2) Mg3P2
Example 2:
copper (III) chloride
Step 1) Cu3+ Cl1Step 2) CuCl3
Instructions
for:
Naming
Compounds
2 Non-metals
(share electrons)
Prefix List:
1 = mono (not used for the first
element)
2 = di
3 = tri
4 = tetra
5 = penta
6 = hexa
7 = hepta
8 = octa
9 = nona
10 = deca
NOTE 1: The charges are their singles sign! They are
trying to let the other atoms know, “Hey, I have electrons
available (+)...”, or “Hey, I need some electrons to
become stable (-)…” Once they have bonded, the charges
cross over to become the subscripts indicating the number
of atoms the other element needs to make the bond work!
Example 1:
tricarbon tetrafluoride
C3F4
NOTE 2: Subscripts that are the same will always reduce,
and it is not necessary to write “ones” for ionic
compounds.
Name the metal (+ cation); add –ide ending to the nonmetal (- anion).
NOTE: DO NOT reduce
subscripts for covalent
compounds.
Use the subscript in the
compound to indicate the prefix
to be added to the name of the
element.
Example1: CaBr 2= calcium bromide
SrF2 = strontium fluoride
Example 2: FeCl3 = iron (III) chloride
NOTE 1: Always use (Roman Numerals) after transition
metals to indicate their oxidation number, by uncrisscrossing the subscripts.
NOTE 2: Prefixes are NEVER used in ionic compounds;
subscripts are not reflected in their name.
Example 2:
bicarbon dichloride
C2Cl2
Example 1:
Si2O3
disilicon trioxide
NOTE: If there are two vowels
in a row due to the addition of a
prefix, one vowel gets dropped.
Example 2: instead of
tetraoxide, it would be
tetroxide.
NOTE 1: Protect the existing subscripts on
polyatomic ions by placing parenthesis around
them when adding additional subscripts. You
can NEVER change existing subscripts!!
Example 1:
ammonium sulfate
Step 1) NH41+ SO42Step 2) (NH4)2SO4
Example 2:
copper (II) nitrate
Step 1) Cu2+ NO31Step 2) Cu(NO3)2
NOTE 2: Subscripts that are the same will
always reduce, and “ones” are not necessary to
write.
Example 1:
Hydrofluoric Acid =
HF
Example 2: Sulfurous
Acid = H2SO3
Example 3:
Phosphoric Acid
H3PO4
=
Ex) 1: hydro – (stem) – ic acid = anion: stem with –ide ending
Ex) 2: (stem) – ous acid = anion: stem with –ite ending
Ex) 3: (stem) – ic acid = anion: stem with –ate ending
Name the metal or polyatomic ion serving as
the cation; keep the name for the polyatomic
ion, or add –ide ending to a non-metal, for the
anion.
Example 1:
(NH4)2Cr2O7 and (NH4)2S
would be ammonium dichromate
and ammonium sulfide
Example 2:
CrSO4
chromium (II) sulfate
(Look up charge for sulfate then determine
what charge chromium must have to cancel it
out.)
1. Figure out the
name of the anion
(what is bonded
to hydrogen) by
looking at
periodic table or
list of polyatomic
ions.
2. See rules for
naming acids,
based on the
name of the
anion. (See
examples above)