Chemical Formulae
• Ionic versus Molecular/Covalent
– Ionic compounds typically feature a metal
(cation) and a nonmetal (anion).
– Molecular compounds are composed of
nonmetals exclusively.
– Both must be electrically neutral in charge.
– Nomenclature (naming) has similarities… the
differences occur because of the law of multiple
proportions.
• The same elements can make multiple, different
compounds... Roman numerals or prefixes are used.1
Molecular Formulae
• Formula Structure
– Elements present
– Subscripts* (shows how much of each
element)
CO2
This is carbon dioxide
*
If no subscript is present it means
that there is only one atom of that
element
This is a molecule of a molecular compound
2
Molecular Nomenclature
Naming Rules
– Write the names of both elements.
• You will only learn covalent naming for binary
compounds
– Change the ending of the second element to ide.
– Add prefixes to each element to indicate the
subscripted number of atoms present.
• If the first element only has one
atom then
no prefix
carbon
dioxide
oxide
oxygen
is added.
Example: CO2 becomes
3
Molecular Nomenclature
•
Prefixes
- Greek prefixes used…
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
monodi–
tritetrapentahexaheptaoctanonadeca-
- The final “o” or “a” of the prefix is usually dropped
when preceding an element beginning with a vowel.
4
Molecular Compound
Formulae
(Molecules)
B3+ C4+ C4C2+ C2- N3+ N3- N5+
N4+ N2+ O2- O1- F1- Si4+
Si2+ P5+ P3+
P3- S6+
2- Cl1+
S4+ S2+
S
As2Se
As
AsBr
As
AsCl
S35343533
As
AsF
AsI
S
242Se
3O
17+
5+ Cl3+
diarsenic
Cl Cl
Cl
diarsenic
arsenic
arsenic
arsenic
tetraarsenic
arsenic
monoseleni
As3+
As3pentasulfide
tribromide
trifluoride
triselenide
trichloride
pentoxide
trisulfide
pentachloride
tetrasulfide
triiodide
trioxide
de
As5+ Se4+
Se6+
Se2- Br1+
Br1Br7+
Br5+ Br3+ Te4+ Te6+ Te2- I7+
I5+ I1+ I1- At1+ At1- At7+
At5+ At3+
5
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Molecular Compound
Formulae
(Molecules)
B3+ C4+ C4C2+ C2- N3+ N3- N5+
N4+ N2+ O2- O1- F1- Si4+
Si2+ P5+ P3+
P3- S6+
2- Cl1+
S4+ S2+
S
B
BBr
BCl
BF
Cl
C334
B
BN
224O33
17+
5+ Cl3+
Cl Cl diboron
Cl
tetraboron
diboron
boron
boron
boron nitride
trioxide
3+
monocarbide
tetrachloride
tribromide
trichloride
trifluoride
As
As3As5+ Se4+
Se6+
Se2- Br1+
Br1Br7+
Br5+ Br3+ Te4+ Te6+ Te2- I7+
I5+ I1+ I1- At1+ At1- At7+
At5+ At3+
6
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Molecular Compound
Formulae
(Molecules)
B3+ C4+ C4C2+ C2- N3+ N3- N5+
N4+ N2+ O2- O1- F1- Si4+
Si2+ P5+ P3+
P3- S6+
2- Cl1+
S4+ S2+
S
CCl
CSe
CN
CO
CF
CO
CS
CI
4422
442
17+
Cl Cl
Cl5+ Cl3+
carbon
carbon
carbon
carbon
tetrachloride
tetranitride
diselenide
dioxide
tetrafluoride
tetraiodide
monoxide
disulfide
As3+
As3As5+ Se4+
Se6+
Se2- Br1+
Br1Br7+
Br5+ Br3+ Te4+ Te6+ Te2- I7+
I5+ I1+ I1- At1+ At1- At7+
At5+ At3+
7
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Molecular Compound
Formulae
(Molecules)
B3+ C4+ C4C2+ C2- N3+ N3- N5+
N4+ N2+ O2- O1- F1- Si4+
Si2+ P5+ P3+ Cl O
P3- S6+
2
2- Cl1+
ClO
ClF
S4+ S2+
S
2
dichlorin
ClF
Cl2O
37
chlorine
chlorin
17+
Cl Cl
Cl5+ Cl3+
dichlorine
chlorine
e
monofluorid
e
3+
3trifluoride
heptoxide
monoxid
As
As
dioxide
e
4+
5+
e
As Se
Se6+
Se2- Br1+
Br1Br7+
Br5+ Br3+ Te4+ Te6+ Te2- I7+
I5+ I1+ I1- At1+ At1- At7+
At5+ At3+
8
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Molecular Compound
Formulae
(Molecules)
B3+ C4+ C4C2+ C2- N3+ N3- N5+
N4+ N2+ O2- O1- F1- Si4+
Si2+ P5+ P3+
P3- S6+
2- Cl1+
GeCl
IF
ICl
S4+ S2+
S
5 4
7
GeF
IF
O
O35242
GeCl
F
H
ICl
O
222
germanium
iodine
iodine
17+
Cl Cl
Cl5+ Cl3+
germanium
diiodine
dihydrogen
fluoride
iodine
pentafluorid
heptafluorid
monochlorid
tetrachlorid
3+
3tetrafluoride
pentoxide
trichloride
monoxide
dichloride
dioxide
As
As
eee
4+
5+
As Se
Se6+
Se2- Br1+
Br1Br7+
Br5+ Br3+ Te4+ Te6+ Te2- I7+
I5+ I1+ I1- At1+ At1- At7+
At5+ At3+
9
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Molecular Compound
Formulae
(Molecules)
B3+ C4+ C4C2+ C2- N3+ N3- N5+
N4+ N2+ O2- O1- F1- Si4+
Si2+ P5+ P3+
P3- S6+
2- Cl1+
S4+ S2+
S
NN
NCl
NO
NH
NO
S
N
NF
O323454
424Se
2O
17+
Cl Cl
Cl5+ Cl3+
tetranitrogen
dinitrogen
nitrogen
tetraselenide
tetrasulfide
pentoxide
trihydride
chloride
dioxide
monoxide
fluoride
As3+
As3As5+ Se4+
Se6+
Se2- Br1+
Br1Br7+
Br5+ Br3+ Te4+ Te6+ Te2- I7+
I5+ I1+ I1- At1+ At1- At7+
At5+ At3+
10
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Molecular Compound
Formulae
(Molecules)
B3+ C4+ C4C2+ C2- N3+ N3- N5+
N4+ N2+ O2- O1- F1- Si4+
Si2+ P5+ P3+
P3- S6+
2- Cl1+
PP44Se
S33
S4+ S2+
S
P22Se
O
S5353535
PCl
PH
PF
P
tetraphosphoru
17+
Cl Cl diphosphorus
Cl5+ Cl3+
phosphorus
phosphorus
phosphorus
s
3+
3trichloride
pentasulfide
pentoxide
pentachloride
pentafluoride
trifluoride
trihydride
pentaselenide
trioxide
As
As
trisulfide
4+ triselenide
5+
As Se
Se6+
Se2- Br1+
Br1Br7+
Br5+ Br3+ Te4+ Te6+ Te2- I7+
I5+ I1+ I1- At1+ At1- At7+
At5+ At3+
11
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Molecular Compound
Formulae
(Molecules)
B3+ C4+ C4C2+ C2- N3+ N3- N5+
N4+ N2+ O2- O1- F1- Si4+
Si2+ P5+ P3+
P3- S6+
2- Cl1+
S4+ S2+
S
S
Se
SeCl
SeF
Cl
SeS
22Cl
SeO
SO
SF
SO
22
424
6
342
17+
5+ Cl3+
Cl Cl
Cl
disulfur
diselenium
selenium
sulfur
sulfur
dichloride
As3+
As3tetrachloride
tetrafluoride
disulfide
hexafluoride
dioxide
trioxide
As5+ Se4+
Se6+
Se2- Br1+
Br1Br7+
Br5+ Br3+ Te4+ Te6+ Te2- I7+
I5+ I1+ I1- At1+ At1- At7+
At5+ At3+
12
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Molecular Compound
Formulae
(Molecules)
B3+ C4+ C4C2+ C2- N3+ N3- N5+
N4+ N2+ O2- O1- F1- Si4+
Si2+ P5+ P3+
P3- S6+
2- Cl1+
S4+ S2+
S
Si
SiCl
SiO
SiS
SiF
SiO
SiC
TeCl
TeI
3N44
244
2
17+
Cl Cl
Cl5+ Cl3+
trisilicon
silicon
tellurium
monocarbide
tetrafluoride
tetranitride
monoxide
disulfide
dioxide
tetrachloride
tetraiodide
dichloride
As3+
As3As5+ Se4+
Se6+
Se2- Br1+
Br1Br7+
Br5+ Br3+ Te4+ Te6+ Te2- I7+
I5+ I1+ I1- At1+ At1- At7+
At5+ At3+
13
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