Naming Ionic Compounds
Chapter 4, Section 3
Compound Names
and Formulas
Model Molecule:
Sodium Chloride
Cation name “regular”
Anion name gets -ide
ending
Covalent Bonds
Prefixes for Covalent
Compounds
Model Molecule:
1 Mono
6 Hexa
Carbon Monoxide
2 Di
7 Hepta
These compounds are named
3 Tri
8
using prefixes to show number of
atoms.
4 Tetra
5 Penta
Transition Metals
These are the metals on the “bridge” or
short part of the periodic table, running
along the center.
These metals can have more than one
charge. Sometimes, for example, iron (Fe)
gives up 2 electrons, and sometimes 3.
Octa
9 Nona
10 Deca
If it helps,
Think about some
brave Roman soldiers,
fighting to the death
on a bridge - each
man wielding a metal
sword and a metal
shield.
1
Roman Numerals
1=I
2 = II
3 = III
4 = IV
“Iron Oxide”
In FeO, the oxygen has a valence of 6,
and so it takes two electrons, giving it a 2charge.
It gets the two electrons from the one
iron atom - so the iron atom must have a
2+ charge.
This makes the name iron (II) oxide,
where the Roman numeral II indicates
that the charge is 2+
FeI2
Transition Metals, con.
So iron can form both FeO and Fe2O3,
depending on the number of electrons the
iron atoms gave up. In order to identify
which “iron oxide” you’re talking about,
you have to use Roman numerals to
indicate the charge of the cation in the
compound.
Iron Oxide
In Fe2O3, the 3 different oxygen atoms
would each take 2 electrons, for a total of
6 Where did they get them?
From the 2 different iron atoms. If the
total number of electrons taken is 6, then
the total number of electrons given must
be 6.
So gave up 3 electrons each.
each of the two iron atoms
MnF3
Fe is a transition metal, so it can have
more than one possible number of
valence electrons.
But Iodine is a halogen, so it definitely
has a valence of 7, so it will take 1
electron.
There are two iodines in the formula, and
each of them must have taken 1 electron,
for a total charge of 2 So it must be iron (II) iodide
Manganese (not magnesium!) is a
transition metal. Flourine is a halogen,
(1-)
If each of the 3 fluorines took 1 electron,
the manganese atom must have given up
3.
So it’s
manganese (III) fluoride
2
Another Example
Cross your heart!
What is the formula for aluminum fluoride?
CaCl2
Aluminum has 3 valence electrons, for a charge
of 3+
Fluorine, a halogen, has a valence of 7, so it
wants one more electron, for a charge of 1 It will take 3 fluorines to take all 3 of the
aluminum valence electrons, so the formula will
be AlF3
Al2O3
Al2O3
3