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Chemical Formulas
and
Nomenclature
CHAPTER 7
In the next few slides we will be looking at
how to write formulas and names for three
different types of chemical compounds:
• 1. IONIC COMPOUNDS
• 2. MOLECULAR COMPOUNDS
• 3. ACIDS
*Each type will have a set of rules that we
must follow to correctly represent the
substance.
What can you tell us about bonds between atoms?
Notes Sheet 4
ionic
PC
NPC
metallic
electrons are transferred
polar covalent (unequal share)
nonpolar covalent (equal share)
electrons are “delocalized”
*electronegativity measures
“electron pull” in a bond
2.3
1.9
0.5
ionic
PC
PC
1.3
1.3
2.2
PC
PC
ionic
0
0.4
0.2
NPC
PC
NPC
How do we begin to write ionic
FORMULAS?
Because atoms want to reach an octet of
outer electrons, the positive or negative
charges (oxidation numbers) can be predicted
for single (monatomic) atoms.
But HOW do we predict the charges
(oxidation numbers) of monatomic ions?
0
1+
Because
an1Ohhh,
metalswant
tendto
toreach
have
2+ atoms
3+
3- 2octet numbers.
positive oxidation
of outer electrons,
the positive
(lose e-)
variescharges
+1 totend
+7 (oxidation
or negative
Nonmetals
to have
numbers)
can be
predicted for
negative
oxidations
single
(monatomic)
numbers.
(gain atoms.
e-)
varies
We use these charges to create “neutral” compounds…
Why is aluminum oxide Al2O3?
Criss Cross Method of Writing
Formulas
• This method crosses charges and subscripts
to form neutral compounds.
Al +3 and O-2
Al
and O
Al2O3
(neutral)
How do we write oxidation
numbers for transition elements?
The charges on transition metal ions must be
indicated. One method is shown here:
The Roman numeral (stock system) gives
the charge (oxidation number) of the cation:
Ex: Nickel (II) is Ni+2
Nickel (III) is Ni+3
Hey, What are Polyatomic Ions?
Criss-Cross Method of Writing
Formulas….
Notice a trend between the oxidation/charges
of ions and the subscripts of elements.
Ex:
Al+3 and SO4-2 gives
Al2(SO4)3
Naming Overview…
metal + nonmetal (cation followed
by anion)
cation = element name
anion = element root-ide
Metal/polyatomic ion + NM/polyatomic ion
cation followed by anion
cation = element or polyatomic ion name
anion = element or polyatomic ion name
cation = element (charge)
using roman numerals
anion = same as above
Naming Ionic Compounds
Ex:
Al2O3
Aluminum and Oxygen
Aluminum oxide
cation
anion
Naming ionic compounds
RECALL:
metal + nonmetal
cation followed by anion
cation = element name
anion = element root-ide
Na+
Cl-
sodium chloride
Li+
H-
lithium hydride
Ca2+
S-2
Al3+
Claluminum chloride calcium sulfide
Mg2+
O-2
magnesium oxide
Na+
N-3
sodium nitride
Naming Ionic Compounds with Polyatomic Ions
RECALL:
cation = element name OR
polyatomic name
anion = element root-ide OR
polyatomic name
Na+
SO42sodium sulfate
iron(II) nitrate
sodium perchlorate
K+
H2PO4potassium dihydrogen phosphate
Naming Ionic Compounds with Transition Metals
RECALL:
cation = element (charge)
anion = element root-ide
Cu+
Clcopper(I) chloride
Hg2+
O2mercury(II) oxide
Fe3+
O2-
Pb2+
Cl1iron(III) oxide
lead(II) chloride
Co2+
Br1Mn4+
O2manganese(IV) oxide cobalt(II) bromide
Formula?
Notes sheet 5
Practice Naming Ionic
Compounds
EX: AgCl is __________________
Silver chloride
Na2O is ___________________
Sodium oxide
CaBr2 is ___________________
Calcium bromide
PbO2 is ___________________
Lead (IV) oxide
Practice Naming Ionic
Compounds
Ex: Li2CO3 is ____________________
Lithium carbonate
Ba(OH)2 is ___________________
Barium hydroxide
Zn(NO3)2 is __________________
Zinc nitrate
KClO3 is ___________________
Potassium chlorate
Naming continued…
Name the following compound:
Ba(Na)2
BaNaNa!
How do we write oxidation
numbers for transition elements?
The oxidation number of a transition element
can be determined by TWO methods.
1. The Roman numeral (stock system)
indicating the charge (oxidation number).
Ex: iron (II) is Fe+2
iron (III) is Fe+3
2. The suffix ending (old system):
Ex: ferrous is Fe+2
ferric is Fe+3
Notes Sheet 5
Lower ion charge
= root -ous ending
chromous oxide
chromium (III) oxide
cobaltous chloride
cobalt (III) chloride
lead (II) chloride
mercury (I) chloride
plumbic chloride
mercuric oxide
Higher ion charge
= root -ic ending
Naming Binary Molecular
Compounds
• Unlike ionic compounds, molecular
compounds are composed of individual
covalently bonded units, or molecules.
• Covalent compounds are formed between
nonmetals.
• Prefixes are used to indicate number of
each type of element in the compound.
• Write the prefixes as indicated on the next
slide….
Molecular Prefixes
1
mono-
6
hexa-
2
di-
7
hepta-
3
tri-
8
octa-
4
tetra-
9
nona-
5
penta-
10
deca-
(decade)
Naming covalent compounds
monotri-
pentahexa-
octa-
deca-
-use prefixes for each element
-“mono” left off for FIRST element
-double vowels usually drop (a)
phosphorous pentachloride
sulfur hexafluoride
sulfur dioxide
sulfur trioxide
carbon dioxide
tetraphosphorous decoxide
dinitrogen pentoxide
dichlorine heptoxide
hydrogen peroxide
methane
nitrous oxide,
laughing gas
N2H4
CCl4
P2O3
Cl2O7
CO2
CS2
IF
NI3
H2O
PH3
NH3
RECALL:
All non-metals!
Named similarly to binary ionics…
…but now prefixes are used.
“mono-” is never used for 1st element
dinitrogen
monoxide
phosphorus
trichloride
sulfur
hexafluoride
dinitrogen
pentoxide
suflur
dioxide
hydrogen
peroxide
Practice Naming Binary
Molecular Compounds
Ex: SO3 is ____________________
sulfur trioxide
PBr5 is ____________________
phosphorus pentabromide
ICl3 is _____________________
iodine trichloride
H2O is _____________________
dihydrogen monoxide
Sb2O3 is _____________________
diantimony trioxide (*metalloid)
Strange Names for Molecules
BUCKMINSTER
FULLERENE
MORONIC ACID
ARABITOL
CRAPINON
MEGAPHONE
BUTANAL
Add to NOTES PACKET CONTENT!
Looks like “H + anion”
Name is based on anion suffix.
“-ate” → “-ic acid”
“-ite” → “-ous acid”
“-ide” → “hydro-____-ic acid”
perchloric acid
hypochlorous acid
sulfuric acid
hydrocyanic acid
hydrochloric acid
nitric acid
Practice Naming Acids
What are the names of acids formed from the
nitrite and nitrate ions?
Ex: HNO2 is nitrous acid
HNO3 is nitric acid
What are the names of acids formed from
sulfite and sulfate ions?
Ex: H2SO3 is sulfurous acid
H2SO4 is sulfuric acid
Practice
CaSO4
calcium sulfate
AlCl3
CrF2
aluminum chloride chromium(II) fluoride
CO2
carbon dioxide
HCN
hydrocyanic acid
K2O2
potassium peroxide
N2O4
KClO3
NiBr2
dinitrogen tetroxide potassium chlorate nickel(II) bromide
LiCl
lithium chloride
MgO
P2O5
magnesium oxide diphosphorus pentoxide
Ag3PO4
silver phosphate
CH4
methane
Fe2O3
iron(III) oxide
PRACTICE SITES
• Matching nomenclature
http://www.zerobio.com/drag_gr9/chem.ht
m
THE END