Polyatomic Ions and Molecular
Nomenclature
Lesson 15
October 25th, 2010
Polyatomic Ions
Ions that are composed of one atom are
called monatomic ions.
 Monatomic Ion- an ion composed of only
one atom.


We have only looked at these so far
Polyatomic Ions

Polyatomic Ions are ions that are
composed of more than one atom. The
entire molecule carries a charge to it. Example
NO3-
SO42-
O
PO43-
2-
O
O S O
O P O
O
O
3-
Bonding

Ionic Bonding with polyatomic ions occurs in
the same manner as it does with standard
ionic molecules.
 - Use the crossover method
 - Be sure that the charge that is crossed
over applies to the whole polyatomic ion. If
the charge is greater than 1, use brackets
around the polyatomic ion to indicate the
number applies to the whole ion.
Example 1
Step 1
Na + NO3-
Step 2
1+
Na
Step 3
1- 1+
NO3 Na
1NO3
Step 4
NaNO3
Example 2
Step 1
Mg + NO3-
Step 2
2+
Mg
1NO3
Step 3
2+
Mg
1NO3
Step 4
Mg (NO3)2
Practice
Mg + ClO3- =
Na + SiO32- =
Fr + HS- =
NH4+ + Cl =
Li + Cl =
Be + O22- =
Sr + PO43- =
Al + BO33- =
Al + SO42- =
Na + OH- =
Naming Ionic Polyatomic
compounds: IUPAC
Multivalent: Metal (charge) polyatomic
ion
 Monovalent: Metal polyatomic ion


Tertiary ionic compounds are comprised of a
metal ion and a polyatomic ion. Write the
polyatomic ions in the same way as
monatomic ions.
Examples

NaOH =


Cu(ClO4)2 =


sodium hydroxide (NOT MULTIVALENT)
copper (II) perchlorate
Tin (IV) chlorate =

Sn (ClO3)4
Practice
Copper (I) hydroxide =
Aluminum sulfate =
= Cu+ OH-
Al3+ SO43-
=
= AlSO
4
CuOH
CrCO3 =
Cr2(CO3)3 =
Cr2+ CO32-
Cr3+ CO32-
=Chromium (II) Carbonate
Chromium (III) Carbonate
Naming Binary Molecular
Compounds: IUPAC
1.
2.
Write down the name of the first element. If
there is more than one atom of this element
attach a Greek prefix. (if there is only one
atom do not attach the prefix)
Attach a Greek prefix (relating to the
number of atoms) to the second elements
name and add -ide.
Prefixes
# of
atoms
1
2
3
4
5
6
7
8
9
10
Prefix
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
Example:

CO = Carbon monoxide

CO2 = Carbon dioxide
Additional Rules

Elements that are commonly bonded to
themselves in nature do so to make
themselves more stable. These molecules
are known as diatomic Molecules. Some
common examples include (O2, H2, N2, Br2,
Cl2, S8). When we name them they retain
their element name without the use of
prefixes. Example.
O2 is not dioxide. It is
just Oxygen gas.
Practice

HF = Hydrogen monofluoride

PBr =Phosphorous monobromide

carbon tetrafluoride = CF4

Silicon dibromide =SiBr2
Complete all of the
practice Questions

Unit Test On Thursday