Learning Objectives:
What is a polyatomic ion?
How do polyatomic ions combine with
other ions?
How are compound names determined?
6.1 POLYATOMIC IONS – STUDENT NOTES,
monatomic
Polyatomic
ions
Negative
positive
The prior ions in the notes were all charged single atoms. These are called ____________ ions.
The other important class of ions includes groups of atoms that act together to create ions and ionic bonds.
Since these are ions made of many atoms they are called____________ ________.
The majority of polyatomic ions have a ___________ charge but there is one with a positive charge.
REPRESENTING POLYATOMIC IONS:
Polyatomic ions are represented with square brackets to
illustrate that they are a group that acts as a unit. The charge is included in the upper right.
(Fill in the remaining boxes in the following table)
Name
Ammonia Ion
Nitrate Ion
Sulfate Ion
Lewis Structure
Formula
Charge
NH4 1+
1+
WHEN POLYATOMIC IONS COMBINE
When polyatomic ions combine with other ions to create
stability they follow the same rules as all ions. They combine to create a neutral compound. If more than one of a
polyatomic ion is included in a combination it is placed in parenthesis. A subscript outside the parenthesis indicates the
number of the polyatomic ion included in the structure.
Answer the questions below related to the Formula for Calcium Nitrate:
How many Calcium atoms are present? ________
How many Nitrogen atoms are present?________
Now many Oxygen atoms are present? _________ How many Nitrate Ions are present? ___________
NAMING IONIC COMPOUNDS
* Names have two parts: 1st part for Cation, 2nd Part for Anion
*Anions change their suffix to –ide
* Anions students need to know for this class are:
Fluorine becomes Fluoride, Chlorine becomes Chloride, Bromine becomes Bromide,
Iodine becomes Iodide, Oxygen becomes oxide , Sulfur becomes Sulfide
EXAMPLES:
CaBr2 is named Calcium Bromide
MgF2 is named Magnesium Fluoride
WHEN THE CATION IS A TRANSITION METAL
Transitions metals form multiple cations
EXAMPLE: Copper forms Cu2+ and Cu1+
Rules are the same as before except the cation (+ ion) includes roman numeral in parentheis to indicate
1+
2+
its charge. Copper (I) for Cu and Copper (II) for Cu .
EXAMPLES: CuCl is named Copper (I) Chloride
CuCl2 is named Copper (II) Chloride
POLYATOMICS If polyatomic anion (or cation) is present simply use its name:
(NH4)2SO4 = Ammonia Sulfate
Name the following:
CaCl2
CaI2 (I = Iodine)
Cation
Calcium
Cation
Calcium
Anion
Chlorine
Name: Calcium Chloride
Anion
Chlorine
Name: Calcium Iodide
NAMING MOLECULAR COMPOUNDS - The name and formula of a molecular compound describe the
type and number of atoms in a molecule of a compound.
These rules are general rules which means they are not strictly followed so there will be
cases where the rules don’t apply. For the purpose of this course the rules will always
apply. Example CO2
First Part
Second Part
nd
*Most metallic atom comes first
* 2 element is given an ending of
*If the 2 two elements are in the same
IDE
group the one closest to the bottom
* Prefixes are added to indicate the #
comes first.
of the element present
* Prefixes are added to indicate the # of
the element present (most of the time)
Carbon
Prefixes for Naming
Compounds
# of
Atoms
Di Oxide
Name is Carbon Dioxide
1
2
3
4
5
6
7
8
9
10
Prefix
MonodiTriTetraPentaHexaHeptaOctaNonaDeca-
Which compound is dinitrogen tetroxide? A or B
Which compound is nitrogen dioxide? A or B
EXAMPLE OF A COMPOUND THAT DOES NOT FOLLOW THE RULES: What would water be called if it followed
the rules? Why is it not called this?