Download 2 - Old Saybrook Public Schools

Writing Formulas and Naming
Compounds
WHAT DO ALL THESE THINGS HAVE IN COMMON?
Oxidation and Reduction
0
2Na
+
+1
-1
0
Cl2 2NaCl
 Oxidation is loss of electrons or…
Oxidation
Is
Losing
(Half reaction)
0
+1
Na 1e- + Na
Na is oxidized.
Oxidation and Reduction
0
2Na
+
+1 -1
0
Cl2 2NaCl
 Reduction is gain of electrons or…
(Half reaction)
0
Cl
+
-1
1e-Cl
Cl is reduced.
Reduction
Is
Gaining
Here’s a little
trick
Secret Agent Man
OIL
RIG
 Oxidizing agent (O.A.)
causes a particle to lose e- (by gaining e- itself) Cl
 Reducing agent (R.A.) causes another
particle to gain e- (by losing e- itself)
Particle
Oxidized
Particle
Reduced
R.A.
O.A.
0
2Na
+
Na
0
+1
-1
Cl2 2Na Cl
0
2Na
+
0
+1
-1
Cl2 2Na Cl
The particle oxidized and the particle reduced are
ALWAYS on the same side of the equation!
AND the oxidizing agent and reducing agent
are ALWAYS on the same side of the equation
OIL
RIG
So happy togetherrrrrr!
 Oxidation and reduction always occur
together
Practice
OIL 0
RIG0
+2 -2
Ca
+
S
Ca
S
R.A.
O.A.
1. Assign charges. Then identify:
2. Particle oxidized ____
Ca 3. Particle reduced ____
S
RIG
OIL
4. Oxidizing agent _____
5. Reducing agent ____
S
Ca
O.A.
R.A.
Practice
OIL 0
RIG
0
+2
-1
Mg
+
Cl
Mg
Cl
2
2
R.A.
O.A.
1. Assign charges. Then identify:
2. Particle oxidized ____
Mg 3. Particle reduced ____
Cl
OIL
RIG
Cl 5. Reducing agent ____
4. Oxidizing agent _____
Mg
R.A.
O.A.
Oxidation States
 Oxidation states indicates how many e- are
gained, lost, or shared.
Oxidation states
+2
-1
Mg Cl2
Rules for Naming Oxidation States
 1. In their compounds, the metals of Group
1A always have an oxidation number of +1,
the charge on their ions
+1 -1
NaBr
 2. The oxidation number of fluorine (F) is -1
when it is in a compound.
+1 -1
CuF
Rules for Naming Oxidation States
 3. The oxidation number of a monatomic ion
is equal to its charge.
Fe+3….Oxidation # = +3
Rules for Naming Oxidation States
 4. The sum of the oxidation numbers of all the
atoms in the formula of a compound is equal
+1 -2
to zero.
K2Se
+1(2) + -2 = 0
+2 + -2 = 0
 5. In their compounds, the metals of group 2A
always have an oxidation number of +2, the
charge on their ions.
+2 -2
CaS
+2 + -2 = 0
Rules for Naming Oxidation States
 6. In compounds, the oxidation number of
oxygen is almost always -2. (Exception:
peroxides such as H2O2 or Na2O2 where
oxidation number is -1
+1 -1
+1 -1
Na2O2
2(+1) + 2(-1) = 0
+2 + -2 = 0
H2O2
2(+1) + 2(-1) = 0
+2 + -2 = 0
Rules for Naming Oxidation States
 7. The oxidation number of an atom of a free
element is zero.
Na0
Br20
 8. Hydrogen has an oxidation number of +1 in
all compounds, except the metal hydrides, like
LiH or CaH2, where oxidation number is -1.
+1 -1
+1 -1
HF
KH
Metal hydride
Rules for Naming Oxidation States
 9. In combinations involving nonmetals, the
oxidation number of the less electronegative
element is positive and of the more
electronegative element is negative.
+4 -2
SO2
+4 + 2(-2) = 0
+4 + -4 = 0
+2
-3
Fe3P2
3(+2) + 2(-3) = 0
+6 + -6 = 0
Polyatomic Ions
 Some covalently bonded groups of atoms act
like single atoms in forming ions.
 These charged groups of covalently bonded
atoms are called radicals or polyatomic ions.
SULFITE:
SO3-2
SULFATE: SO4-2
CHLORITE: ClO2-1
CHLORATE: ClO4-1
CHROMATE: CrO4-2
AMMONIUM: NH4+1
HYDRONIUM: H3O+1
HYDROXIDE: OH-1
CYANIDE:
CN-1
PHOSPHATE: PO4-3
Rules for Naming Oxidation States
 10. The algebraic sum of the oxidation
numbers of the atoms of a polyatomic ion is
equal to its charge.
-2
(SO3 ) = the whole ion (S & 3 O’s) have a
charge of -2
+4 -2 -2
( SO3)
___
+4 + -6 = -2
Practice: assign oxidation states
(numbers).
+1
-1
NaCl
+1 -1 = 0
+2 -2
MgS
+2 -2 = 0
Al
0
+2 -2
ZnO
+2 -2 = 0
0
 H2
+2 -1
CrF2
+2 + 2(-1) = 0
+2 -2 = 0
Practice: Assign oxidation states
(charges).
+1
+3 -2
-1
Fe2O3
HBr
+1 + -1 = 0
+2 -1
+6 + -6 = 0
+1 -1
SrH2 *Metal hydride K O
2 2
+2 + -2 = 0
+2
-1
MnBr2
+2 + -2 = 0
+2 + -2 = 0
+4 -2
NO2
+4 + -4 = 0
*peroxide
Practice: assign oxidation states
(numbers).
-2 +1
(OH) -1
-2 + ___
+1 = -1
+3 -2
(Cr2O4
-2
)
____ + 4 (-2) = -2
___
+6 + -8 = -2
+2
-2
(S2O3)-2
___ + 3 (-2) = -2
___
+4 + -6 = -2
2(___)
+2 + -6 = -2
2(___)
+3 + -8 = -2
Practice: assign oxidation states
(numbers).
+1 +6
? -2
H2SO4
1(2) + 1x + 4(-2) = 0
2 + 1x + -8 = 0
1x + -6 = 0
1x = +6
x = +6
+2 +6 + -8 = 0
+8 + -8 = 0
Practice: assign oxidation states
(numbers).
+1 +7 -2
HClO4
+1 +7 -8 = 0
+1 +6
-2
K2Cr2O7
+2 +12 -14 = 0
1(+1) + 1x + 4(-2) = 0
1 + 1x -8 = 0
1x = +7
x = +7
2(+1) + 2x + 7(-2) = 0
2 + 2x -14 = 0
2x = +12
x = +6
Refresher
 Write down elements with their oxidation
numbers.

*More electronegative is written last.
Al+3 S-2
Al2S3
+1
Rb
-3
N
Rb3N1
=
Al2+3S3-2
2(+3) + 3(-2)
+6 -6 = 0
=
Rb3
+1N-3
3(+1) + 1 (-3)
+3 -3 = 0
Polyatomic Ions in Compounds
 Potassium + chlorite
K+1 & (ClO2)-1 = KClO2
 Calcium + chromate
+1 -1 = 0
Ca+2 & (CrO4)-2 = CaCrO4
 Magnesium + hydroxide
+2 -2 = 0
Mg+2 & (OH)-1 = Mg(OH)2
*Leave polyatomic in parenthesis!
+2 + 2(-1) = 0
Writing Chemical Formulas
Li+1I-1 LiI
 Li and I
 K and P
K+1P-3 K3P
 Rb and C
Rb+1C-4 Rb4C
 Li and Cr2O7-2
Li+1(Cr2O7)-2 Li2Cr2O7
Naming Compounds
 Is the compound ionic or covalent?
 If there is a metal or polyatomic ion present, the
compound is ionic.
 If not, it will be classified as covalent.
Naming Ionic Compounds
 1. Binary compounds (2 elements)


A. Name the positive part
B. Follow with the root name of the negative
part, ending in –ide (monatomic negative ions
end in –ide)
CaCl2: Calcium Chloride
Mg3N2: Magnesium Nitride
NaF: Sodium Fluoride
Naming Ionic Compounds
 2. If a metallic ion forms more than one ion
(can have more than 1 oxidation #), the name
of the ion includes its oxidation number in
roman numerals in parentheses after the
name of the metallic ion
+1 -1
+2 -2
CuCl:Copper(I)Chloride FeO: Iron(II)Oxide
+2
-1
+1
-2
CuCl2:Copper(II)Chloride Hg2S:Mercury(I)Sulfide
Naming Ionic Compounds
 3. Compounds containing polyatomic ions

Name the positive part followed by the name
of the negative part
LiNO3: Lithium Nitrate
Na2SO3: Sodium Sulfite
K2SO4: Potassium Sulfate
CuNO3: Copper (I) Nitrate
FeSO4 Iron (II) Sulfate
Naming Covalent Compounds
(2 Nonmetals)
 1. Binary compounds end in –ide
 2. However, names include prefixes to
indicate the number of atoms in the
compound (subscript):
Di = 2
Tri = 3
Tetra = 4
Penta = 5
*mono is not used for the first element
because the 1 is understood.
Hexa = 6
Hepta = 7
Octa = 8
Nona =9
Deca = 10
Let’s try it
CO2 Carbon dioxide
SO3 Sulfur trioxide
N2O3 Dinitrogen trioxide
N2O Dinitrogen monoxide
Naming Covalent Compounds
 3. Some covalent compounds are known by
their common names
 H2O
Water
 NH3 Ammonia
 H2O2 Hydrogen peroxide
 CH4 Methane
Carbon monoxide
 CO
Naming Compounds
Ionic
Covalent
(metal & nonmetal)
Nonmetals
Nonmetals & H
2 elements
ends in -ide
2 Elements
ends in -ide
more than 2 elements
(*polyatomic ions)
ends in –ate or –ite
Common
Names
Roman Numeral?
NH3: ammonia
H2O: water
Ex: CO2 = carbon dioxide CH4: methane
No
Yes
P4O10 = tetraphosphorus CO: carbon
monoxide
Only 1 one More than 1 possible oxidation #
decoxide
Use prefixes: di,
Tri, tetra, penta,
Hexa, hepta, octa,
Nona, deca
oxidation # for the metal
for the metal Ex: FeS
Fe could be +2 or +3, S is -2
Fe must be +2: Fe+2S-2 = Iron (II) Sulfide