IONIC
COMPOUNDS:
Names and
Formulas
Naming compounds in
chemistry is called
NOMENCLATURE
There are a few general rules that apply when naming ionic
compounds.
1. Most ionic compounds are also called salts.
2. Most ionic compounds exist as solids and
many dissolve to form aqueous solutions.
3. An ionic compound is made up of a metal and a
nonmetal; metals are located on the left side of the
periodic table and nonmetals are on the right side.
4. The cation (positive ion) is written first followed
by the anion (negative ion).
5. Before naming compounds, you should first
memorize the individual cations and anions.
Nomenclature of ionic compounds
There are two types of ionic compounds depending on
the cations.
•Type 1 or “fixed oxidation state” cations – only form one
cation
•Groups IA to IIIA and the elements silver (Ag), zinc (Zn)
and cadmium (Cd) form only one type of ion each:
– Group IA elements form +1 ions: Li+, Na +, K +,
Rb +, Cs +
– Group IIA elements form +2 ions: Be +2, Mg +2,
Ca +2, Sr +2, Ba +2
– Group IIIA elements form +3 ions: Al +3
– silver ion = Ag +; zinc ion = Zn +2; cadmium ion =
Cd +2
•Type 2 or “variable oxidation state” cations - can form
multiple cations
Monatomic Charges
The charge of the individual ions in a salt should add up
to zero, the overall charge of the compound. For
example NaCl is composed of Na+ ions and Cl- ions.
For every one sodium ion you need one chloride ion (+1)
+ (-1) = 0
Ba2+ and N3- : You need 3 (+2 ) Barium ions to cancel
out the 2 (-3) nitride ions so the overall charge of the
compound is zero.
Nomenclature of binary ionic compounds
Name the metal then the root of the nonmetal + ide ending:
Binary ionic compound ROOTS
Symbol
Element
Root
Anion
Symbol
Anion
Name
Br
Bromine
Brom
Br-
Bromide
Cl
Chlorine
Chlor
Cl-
Chloride
F
Fluorine
Fluor
F-
Fluoride
H
Hydrogen
Hydr
H-
Hydride
I
Iodine
Iod
I-
Iodide
N
Nitrogen
Nitr
N-3
Nitride
O
Oxygen
Ox
O-2
Oxide
P
Phosphorus
Phosph
P-3
Phosphide
S
Sulfur
Sulf
S-2
Sulfide
Nomenclature of binary ionic compounds
NaCl Sodium chloride BaCl2
H2S Hydrogen sulfide Mg3N2
NaF Sodium fluoride
K2O
Barium chloride
Magnesium nitride
Potassium oxide
Notice that the cation is always mentioned first and then the anion.
Notice that the anion always ends in -ide
Notice that the number of elements in the compound is
not mentioned in the name.
Name the following ionic compounds:
Na2O
K2S
CaCl2
AgCl
MgBr2
AlN
Ba3As2
AlH3
ZnI2
Li3P
Nomenclature of binary ionic compounds
Answers:
Na2O = sodium oxide
K2S = potassium sulfide
MgBr2 = magnesium bromide
AlN = aluminum nitride
Ba3As2 = barium arsenide
CaCl2 =
AgCl = silver chloride
AlH3 = aluminum hydride
ZnI2 = zinc iodide
phosphide
calcium chloride
Li3P = lithium
Polyatomic Ions
Ions made up of more than one atom are polyatomic
ions:
The individual ions should add up to the overall charge
of the polyatomic ion.
What is the charge of Mn in MnO4-?
1 Mn + 4 O = -1 so 1(Mn) + 4 (-2) = -1 so Mn - 8 = -1
so Mn = +7
– only one polyatomic cation: NH4 + which is the ammonium
ion
– many polyatomic anions: ……next page (I will give you a list
to memorize)
Note: the polyatomic ions must be memorized.
Nomenclature of binary ionic compounds
Some polyatomic anions that you must know:
NO3- = nitrate
NO2- = nitrite
SO4 2 - = sulfate
SO32- = sulfite
PO43- = phosphate
PO33- = phosphite
CO32- = carbonate
HCO31- = hydrogen carbonate or bicarbonate
OH- = hydroxide
CN- = cyanide
C2H3O2- = acetate
C2O42- = oxalate
Nomenclature of binary ionic compounds
Naming salts composed of the polyatomic ions is the
same as with the monatomic anions. Metal name then
polyatomic name.
NaOH sodium hydroxide
H2SO4 hydrogen sulfate
Ba(NO3)2 barium nitrate
CsNO2
cesium nitrite
Sometimes there is a common name:
KHCO3 potassium hydrogen carbonate or potassium bicarbonate
Name the following ionic compounds:
NaHCO3
K2SO3
MgSO4
Ca(OH)2
NH4NO3
Zn(NO3)2
KCN
Li3PO4
H2PO4
HNO3
Nomenclature of binary ionic compounds
Answers:
NaHCO3
= sodium hydrogen carbonate or sodium bicarbonate
K2SO3
= potassium sulfite
MgSO4
= magnesium sulfate
KCN
= potassium cyanide
H2PO4
= hydrogen phosphate
Ca(OH)2
= calcium hydroxide
NH4NO3
= ammonium nitrate
Zn(NO3)2
= zinc nitrate
Li3PO4
= lithium phosphate
HNO3
= hydrogen nitrate
Early Names of Elements
Present Name
Symbol
Former Name
Antimony
Sb
Stibium
Copper
Cu
Cuprum
Gold
Au
Aurum
Iron
Fe
Ferrum
Lead
Pb
Plumbum
Mercury
Hg
Hydrargyrum
Potassium
K
Kalium
Silver
Ag
Argentum
Sodium
Na
Natrium
Tin
Sn
Stannum
Tungsten
W
Wolfram
Nomenclature of binary ionic compounds
The previous examples only named type 1 or “fixed
oxidation state” cations. When naming type 2 or “variable
oxidation state” cations the rules change.
CuOH copper(I) hydroxide
Fe(NO3)3 iron(III) nitrate
CuSO4 copper(II) sulfate
Sn(NO2)4 tin(IV) nitrite
Sometimes a common name exists:
CuOH cuprous hydroxide
Fe(NO3)3 ferric nitrate
When naming type 2 cations, the systematic method (IUPAC) requires
the use of roman numerals after the elemental name to represent the
oxidation state of the cation. The common name uses the –ic ending
for the higher oxidation state and –ous ending for the lower oxidation
state. Many times the old latin or greek name is used as the root.
Name the following ionic compounds:
CuHCO3
FeSO3
CuSO4
Cr(CN)3
Cr(PO4)2
Sn(OH)2
W(NO2)5
Ti(CO3)2
CoPO4
PbCl2
Nomenclature of binary ionic compounds
Answers:
CuHCO3 = copper(I) hydrogen carbonate or cuprous bicarbonate
FeSO3
= iron(II) sulfite or ferrous sulfite
CuSO4 = copper(II) sulfate or cupric sulfate
Cr(CN)3 = chromium(III) cyanide
Cr(PO4)2 = chromium (VI) phosphate
Sn(OH)2 = tin(II) hydroxide or stannous hydroxide
W(NO2)5 = tungsten(V) nitrite
Ti(CO3)2 = titanium(IV) carbonate
CoPO4
PbCl2
= cobalt(III) phosphate or cobaltic phosphate
= lead(II) chloride or plumbous chloride
PRACTICE PROBLEMS
Below the formula, give the systematic name for the following
compounds. If a common name exist, write it below the systematic
name.
1. KBr
potassium
bromide
2. BaO
3. Na2O
Sodium oxide
Barium oxide
4. CaF3
5. Cr2S3
calcium
fluoride
Chromium
(III) sulfide
6. Ti(NO3)4
Titanium (IV) nitrate
or titanic nitrate
The problem set continues on the next page.
PRACTICE PROBLEMS
Below the name, write the formula for the following compounds.
Lithium chloride
b) Aluminum sulfide e) Copper(II) oxide
Li
Al3+ S2f) + Cl -
LiCl
Iron(III) chloride i)
FeCl3
Potassium nitrite
KNO2
Ammonium carbonates s
(NH4)2CO3
CuO
Al2S3
Calcium bicarbonate l
Ca(HCO3)2
Potassium sulfate
K2SO4
)Iron(II) phosphate w)
Fe3(PO4)2