FORMULA WRITING
NAMING
EQUATIONS & BALANCING
Kenneth E. Schnobrich
Oxidation States & Rules
 Oxidation states can represent the loss and
gain of electrons or the partial loss and gain
of electrons when they are shared
unequally.
 There are some rules that we follow when assigning
oxidation states to the elements represented in the
formula
 When an element is in its elemental state
(uncombined with a different element) it has an
assigned oxidation state of 0.
Rules
 The metals in Group 1 all have assigned oxidation
states of +1 in compounds.
 The metals in Group 2 all have assigned oxidation
states of +2 in compounds.
 Hydrogen, in compounds generally has an
oxidation state of +1.
 Exception - a group of compounds called Hydrides (when
hydrogen is combined with metals from Groups 1 & 2, B, and
Al). In this case it has an oxidation state of -1 because of its
higher electronegativity
 NaH (sodium hydride), CaH2 (calcium hydride)
Rules
 Oxygen has an assigned oxidation of -2 in most
compounds because of its high electronegativity.
 Exception - In a group of compounds called Peroxides it has an
assigned oxidation state of -1. The term Peroxide generally means
one more oxygen than normally found.
 H2O2 (hydrogen peroxide) and Na2O2 (sodium peroxide) are
examples.
 Exception - when oxygen combines with fluorine it has an assigned
oxidation state of +2.
 OF2 - because fluorine is more electronegative
 Fluorine and most of the other halogens have assigned
oxidation states of -1 in binary compounds. This is due to
their electronegativities and the need to gain electrons to
complete the octet in the outer energy level.
Rules
 In Polyatomic Ions the sum of the oxidation states must
equal the charge on the ion (see table E).
 In the SO4-2 ion (sulfate ion) - sulfur is a +6 and O is a -2
 1S(+6) + 4O(-2) = (+6) + (-8) = -2 (the charge on the ion)
 In Compounds the sum of the oxidation states must always
equal 0 because compounds are electrically neutral.
 In Al2(SO4)3 (aluminum sulfate) - Al is +3; S is +6; and O is -2
 2Al(+6) + 3S(+6) + 12O(-2) = (+6) + (+18) + (-24) = 0
Let’s Practice
 For the following polyatomic ions determine
the oxidation state of the underlined
element:
 ClO3-1 (chlorate ion)
 MnO4-1 (permanganate ion)
 MnO4-2 (manganate ion)
 NO3-1 (nitrate ion)
 NO2-1 (nitrite ion)
 PO4-3 (phosphate ion)
Let’s Practice
 For the following compounds determine the
oxidation state of the underlined element:
 K2SO4
 CaMnO4
 Be3(PO4)2
 LiClO4
 CrCl3
 Na2SO3
 NiBr2
Writing a Formula
 It is important for you to remember that when you
are talking about compounds the sum of the
oxidation states must always equal 0.
 We will generally divide compounds into four
major categories:




Salts
Acids
Bases
Other Molecular Compounds (organic compounds generally)
 Compounds can also be divided into binary and
ternary compounds.
Let’s Make Some Distinctions
 Binary Compounds - consist of two different elements
combined in different ratios.
 Note - some ternary compounds are named like binary compounds
 Ternary Compounds - consist of three or more different
elements combined in different ratios.
 Salts - both binary and ternary are combinations of metals
and nonmetals (or nonmetal polyatomic ion).
 Acids - both binary and ternary are combinations of
nonmetals atoms and are generally identified by “starting
with the element hydrogen (H)”.
Let’s Make Some Distinctions
 Bases - are generally combinations of metals and
the nonmetal polyatomic ion OH-1 (hydroxide ion).
Now Let’s Write Formulas
 We will write formulas by categories to help
you differentiate.
 Binary Salts -
Na+1
Combined with
Na2
+1
-2
S
S-2
Swaping oxidation
states method
2(+1) + (-2) = 0
You can also use the lowest common multiple method
Now Let’s Write Formulas
 We will write formulas by categories to help
you differentiate.
 Ternary Salts -
Al+3
Al2+3
-2
SO4
Swaping oxidation
-2
(SO4)3 states method
Combined with
2(+3) + 3(-2) = 0
You can also use the lowest common multiple method
Now It’s Your Turn
 Write correct formulae for each of the following
combinations:
 Ca+2 and F-1
 Al+3 and NO3-1
 Li+1
and O-2
 Ba+2 and PO4-3
 NH4+1and S-2
 Ni+3 and ClO2-1
 Cs+1 and
N-3
Identify each of these as a
binary or ternary compound.
Now It’s Your Turn
 Write correct formulae for each of the following
combinations:
 Ca+2 and OH-1
 H+1 and NO3-1
 Li+1
and OH -1
 H+1 and PO4-3
 H+1 and S-2
 Ni+3 and OH-1
 Cs+1 and
SCN-1
Identify each of these as an
acid, base, or salt.
Now Let’s Name
 The fancy name for naming is of course
nomenclature. We will use the same
classifications that we used for formulas.
 Binary Salts
 Ternary salts
 Binary Acids
 Ternary acids
 Bases
 Other compounds
Binary Salts
 For metals and nonmetals with multiple
positive oxidation states we use the “Stock
System”.
 Check your periodic table and the written formula to
determine the positive (+) oxidation state. When
there is more than one you must indicate that by
using a Roman Numeral in the name enclosed in
parenthesis after the name of the metal or nonmetal.
 If there is only one indicate positive oxidation state
you do not have to do this
Binary Salts (Examples)
 Naming follows the sequence - Metal
(Roman Numeral if necessary) and
nonmetal with the suffix “ide”.
 NaCl = sodium chloride
 K2S = potassium sulfide
 CrF3 = chromium(III) fluoride
 ZnO = zinc oxide
 KCN = potassium cyanide*
 PbI2 = lead(II)iodide
*There are some ternary compounds named like binary compounds
Ternary Salts (Examples)
 Naming follows the sequence - Metal
(Roman Numeral if necessary) and
nonmetal polyatomic ion name.
 NaClO4 = sodium perchlorate
 K2SO4 = potassium sulfate
 Cr(NO3)3 = chromium(III) nitrate
 Zn3(PO4)2 = zinc phosphate
 NH4NO3 = ammonium nitrate
 PbCrO4 = lead(II)chromate
 Co(SCN)2 = cobalt(II) thiocyanate
Naming Binary Acids
 For the naming of binary acids the rules are
relatively simple. It will always be a
combination of hydrogen (H) and some
other nonmetal.
 Binary acids start with the prefix “hydro”
and end with the suffix “ic”. The root of the
name comes from the nonmetal.
 Example: HCl = hydrochloric acid
Name These Binary Acids
in Aqueous Solutions
 Remember - hydro_______ic
 The root is always the name of the anion like
“chlor” from chlorine (drop after the last
consonant).






HF
HBr
HI
H 2S
HCN*
HCl
If the substance is in its gaseous state it is named like a normal
binary compound (I.e. HCl = hydrogen chloride)
Naming Ternary Acids
 While there are 3 or more elements the naming is simple.
The name comes from the anion in the formula.
 If the anion ends in “ate” the acid will end in “ic”
 If the anion ends in “ite” the acid will end in “ous”
 If there is a prefix associated with the anion it is retained
(like - “di”, “per”, “hypo”).
 Examples: H2SO4 - contains the “sulfate” ion so it would
be named sulfuric acid || H2Cr2O7 - contains the
“dichromate” ion so it would be named dichromic acid
Name These Ternary Acids








H3PO4
HNO3
HNO2
HClO
HClO2
HClO4
HMnO4
H2SO3
Please note: Many times there are comparable
acids for elements in the same group - like
H2SeO4, HBrO, HIO4, H3AsO4
Naming Bases (Easy)
 The name of the base comes from the name
of the metal cation and then the “hydroxide”
ion.
 NaOH
 Ba(OH)2
 Co(OH)3
 Al(OH)3
 Fe(OH)2
 Pb(OH)4
sodium hydroxide
barium hydroxide
cobalt (III) hydroxide
aluminum hydroxide
iron (II) hydroxide
lead (IV) hydroxide
Fill-in the Blanks
Name
Formula
Acid/Base/Salt
Sodium chloride
HClO3
Nickel (III) sulfate
LiOH
Hydrosulfuric acid
Acid
Calcium hydroxide
Aluminum chlorate
FeI3
The Other Compounds
There are compounds that do not fall into the
categories we have talked about already. They are
generally combinations of nonmetals and in this case
the nonmetal assigned a positive (+) oxidation state
many times uses the STOCK SYSTEM of naming (the
use of the Roman Numeral to indicate the oxidation
state.
• For Example: CO2 - the common name is carbon
dioxide. The STOCK name is carbon (IV) oxide
because carbon is showing a +4 oxidation state in the
compound.
On the next slide we will illustrate why C is assigned a
+4 oxidation state.
Why Carbon is a +4
Carbon (IV) Oxide
-
-
CO2
EN = 3.5
O
C O
EN = 3.5
EN = 2.6
Carbon is losing partial control of its 4 valence electrons
Name These Compounds
Remember to determine the oxidation state of the nonmetal with a
positive oxidation state - use the rules you learned.
• CO
• SO2
• PCl5
• SO3
• N2O5
• NO2
• NCl3
Reaction Types
 You should be able to indentify the following
types of reactions:
 Combination or Synthesis Reaction
 Decomposition or Analysis Reaction
 Single Replacement Reaction
 Double Replacement Reaction
 Combustion Reactions
 Complete
 Incomplete
Combination (Synthesis)
 In a combination reaction usually two elements
combine to form a compound.
2Na(s) + Cl2(g) = 2NaCl(s)
 To balance the equation you must remember the
Law of Conservation of Matter (# of atoms of each
element must be the same on both sides of the
reaction).
 Note: You can only place coefficients in front of
the given species never in the middle of a formula.
Combination (Synthesis)
 Complete the following combination reactions by
balancing them:
N2(g) + H2(g) = NH3(g)
Al(s) + O2(g) = Al2O3(s)
S(s) + O2(g) = SO3(g)
Decomposition (Analysis)
 More complex compounds breakdown into
simpler substances or elements.
CaCO3(s) = CaO(s) + CO2(g)
 Notice in this case the equation is already
balanced, this will not always be the case.
Decomposition (Analysis)
 Balance the following decomposition
reactions:
HI(g) = H2(g) + I2(g)
N2O5(g) = N2(g) + O2(g)
KClO3(s) = KCl(s) + O2(g)
Single Replacement
 In a single replacement reaction one of the
species in a formula is replaced by another
species:
2NaBr(aq) + Cl2(g) = 2NaCl(aq) + Br2(l)
Single replacement
Mg(s) + 2HCl(aq) = MgCl2(aq) + H2(g)
Single replacement
Single Replacement
 Balance the following single replacement
reactions:
Cu(s) + AgNO3(aq) = Cu(NO3)2(aq) + Ag(s)
Zn(s) + HCl(aq) = ZnCl2(aq) + H2(g)
Zn(s) + H2SO4(aq) = ZnSO4(aq) + H2(g)
Double Replacement
 In a double replacement reaction the
species simply exchange places:
AgNO3(aq) + NaCl(aq) = AgCl(s) + NaNO3(aq)
In this case, when we check both sides of the equation we find that there is
no need to adjust the coefficients - it is balanced
Double Replacement
 Balance the following double replacement
reactions:
Ba(NO3)2(aq) + K2SO4(aq) = BaSO4(s) + KNO3(aq)
Al(NO3)3(aq) + KOH(aq) = Al(OH)3(s) + KNO3(aq)
Cd(NO3)2(aq) + H2S(g) = CdS(s) + HNO3(aq)
Combustion Reactions
 Complete combustion generally involves the
burning of an organic compound in oxygen
to form carbon (IV) oxide and water as
products:
CH4(g) + 2O2(g) = CO2(g) + 2H2O(g)
Combustion Reactions
 Incomplete combustion reactions generally
involve the formation of carbon (II) oxide
and water as products:
2CH4(g) + 3O2(g) = 2CO(g) + 4H2O(g)