SCH 4C
Nomenclature Practice: Molecular Compounds
Molecular compounds share electrons to achieve a stable octet and satisfy the octet rule. Naming
molecular compounds uses the prefix to determine the number of atoms of each element in the
compound.
Use the number of atoms in the formulas to determine the prefixes needed to name the
compounds.
Prefixes

–3
–5
–7
–9
–2
–4
–6
–8
– 10
When there is only one atom of the first element listed, the prefix is dropped.


–1
ie. CO not monocarbon monoxide it is _________________ ______________
When there are two vowels together, drop the first vowel. (Exception: io)

ie. CO not carbon monoxide it is _________________ ______________
Compound Name
Formula
Compound Name
H2S
sulfur hexachloride
PCl3
dichlorine heptoxide
CO
dicarbon dihydride
SF4
dinitrogen monoxide
SO3
silicon tetraiodide
NH3
krypton
pentabromide
SiC
diphosphorus trioxide
H2O
tricarbon octahydride
Formula
arsenic trihydride
C2H4
AsBr3
trioxide
N2O4
carbon tetrachloride
SiO2
selenium dioxide
Nomenclature Practice: Ionic & Molecular Compounds
Fill in the boxes below, but be sure to determine if the compound is ionic or molecular first!
If ionic, find the ion charges, then cross & drop. If molecular, use prefixes to determine the
number of atoms.
Name of
Compound
Formula
ZnCO3
Name of
Compound
Ca(IO3)2
Pb(ClO2)4
MgO
Ca(ClO)2
MgS
H2
AuPO4
Aluminum
hydroxide
dicarbon
tetrahyride
NaHCO3
Cl2
Tin (II) nitrite
NH3
sulfur
hexafluoride
Carbon
tetrachloride
Iron (III) cyanide
PbI4
nickel (II)
bromide
Oxygen gas
cesium
phosphate
Mg(ClO2)2
ammonium
sulfate
cadmium iodide
potassium
permanganate
Formula
N2O5
nitrite
Ag3PO4
SeO2
Name of
Compound
barium
aluminum
chromate
dichlorine
heptoxide
Formula
dinitrogen
monoxide
cobalt (II)
carbonate
Cr(CN)3
Sn(SO4)2
sulfur
trioxide