By: Madi, Caitlin, Safia, and Holly
1. First, write the formula for the
positive ion and write the
formula for the negative ion
second. (POSITIVE goes first,
NEGATIVE goes second)
2. “Criss-cross” the numbers in
front of the charges on the ions.
3. Tidy up the formula in a threepart process:
i) if both subscripts can be
evenly divided by “2” (or “3”),
do so.
ii) omit the subscripted charges
iii) omit any subscript which is
a “1”
Example: Calcium Phosphide
 Calcium Ion= C2+
 Phosphide Ion= P 3 1)Criss cross the charges
2+
C P
 2) C 3 P2
3-
If the first ion in the compound only has one
possible charge, simply write the names of the ions
one after another.
2. If the first ion is a metal known to possess, more
than one possible charge OR a metal which is not on
the table, “un-criss-cross” the subscripts and use
them as charges.
1.
 1) Name the metal ion
 2) look at the periodic table to
see if the metal has more
than one combining capacity
 3) determine the combining
capacity of the metal by
looking at the formula of the
co brackets write compound
 4) in brackets write the
metals combining capacity in
roman numerals
 5) name the non-metal with
the ending “ide”
Example: Cr2 O3
 1) Cr 2+ and Cr3+
23+
 2)Cr 2+O3+ = O and Cr from
un criss crossing the
combining capacity, we can
see that Cr has a combining
capacity of 3+
 3) chromium (III)
 4) chromium (III) oxide
 1) identify each ion and
its charge. Ex chromium
(III) nitride= Cr3+ N3 2) criss cross charges Ex
Cr3+
 3) put the symbols
together and get rid of the
charge values ex Ca3N2
 4) if the subscript ratio is
not the smallest possible
ratio, make them into the
smallest possible ratio Ex
Cr3N3= CrN
Example:
+1
2 1) Cu Se
 2) Criss cross charges
+1
Cu Se
 3) Cu 2 Se
2-
 1)Write the positive ion
name (metal or
ammonium)
- if metal is a multivalent
ion, you must add roman
numerals after the first name in
brackets.
 2)Identify negative ion,
name it and reverse the
criss-cross of the
subscripts.
 Example: Cr(PO4)2
 The symbol “Cr”
translates into: chromate
 Cr(PO4)2 = chromate(II)
PO4 = phosphate
 chromate (II) phosphate
 1) First identify the symbol
 Example:
of the metal and its charge
as well as the ion symbol
and its charge
 2) Criss-cross charges
 3) Put the symbols together,
using the same order as the
name.
 4) Reduce the charge values
chromium (III) sulphate
 Cr 3+ SO4-2
* whole ion has subscript
value
 =Cr2(SO4)3
 *For polyatomic ions use
brackets on (ion)
 1) You identify the two elements in the formula. Find the
symbols for each element.
 2) Write out the symbols in the same order as they came in
the name (make sure to leave a space between when
written out)
 3) Using the prefixes in front of each element find out
which number corresponds to that element.
1
2
3
4
5
6
7
8
9
10
mono
di
tri
tetra
penta
hexa
hepta
octa
nona
deca
 4) Use the corresponding number for each element name
and place it to the bottom right of the symbol from step 1).
 Example: NO
 1 is the subscript for each (*you don’t write mono for the
first element with only one as a subscript)
 NO= nitrogen monoxide
 1) Identify the subscript value of the
first element.
 2) Write down the prefix
corresponding to the subscript of the
first element.
 3) Write down the first atoms name
(the prefix becomes the first syllable of
the element ex. tetrachlorine)
 4)Identify the subscript value of the
second element
 5) Write down the prefix
corresponding to the fifth step.
 6) Write down the seconds atoms
name, ending in “ide” (the prefix
becomes the first syllable of the
element ex. pentaoxide)
Example: N2 O4
di + nitrogen
+
tetra + oxide
dinitrogen tetra oxide
 1) First you name the
 Example: FeSO4
compound as you
normally would
depending on the type of
compound.
 2) After the compound
name, place the
corresponding prefix
(# of water molecules) in
front of the word hydrate.
 Fe= iron (II)
. 5H2O
 SO4= sulphate
 5H 2O = pentahydrate
= iron (II) sulphate
pentahydrate
 1) You write out the
 Example: iron (II)
symbols for the element
sulphate pentahydrate
the ion and the symbol
for water.
 pentahydrate = 5H2O
 2) Next place the number
 sulphate= SO4
correlating with the
2+

iron
(II)
=
Fe
prefix in front of H2O
 3) Reverse criss-cross to
find any combining
capacities.
 4) Write it all out.