WRITING
AND NAMING
IONIC
COMPOUNDS
Formation of Ionic
Compounds
Objectives
• Ionic Compounds
• Formation
• Properties
• Nomenclature
A REMARKABLE FEATURE OF
COMPOUNDS FORMED FROM
ELEMENTS IS THAT THE PROPERTIES
OF THE REACTANT ELEMENTS IS
LOST
+
WHEN AN ATOM LOSES OR
GAINS ELECTRONS IN ORDER
TO ACHIEVE ITS OCTET IT FORMS
AN ION
TODAY IS ALL ABOUT
COMBINING THESE ELECTRICALLY
CHARGED IONS TOGETHER TO
FORM STABLE COMPOUNDS.
REMINDER: WHEN TWO ATOMS
COMBINE TRANSFERRING
VALENCE ELECTRONS IT IS
CALLED AN IONIC BOND.
1
SO WHAT’S
THE BOTTOM LINE?
AN ATOM WILL SHARE, LOSE OR
GAIN ENOUGH ELECTRONS TO
BECOME MORE STABLE WITH
8 ELECTRONS IN ITS OUTERMOST
ENERGY LEVEL.
AND THEN IT WILL BOND WITH
ANOTHER ATOM OF A DIFFERENT
ELEMENT.
THINK ABOUT IT…
FROM OUR PREVIOUS EXAMPLE
SODIUM HAD ONE ELECTRON IN ITS
OUTER SHELL AND GAVE IT AWAY TO
CHLORINE, WHICH WAS IN NEED OF
ANOTHER ELECTRON.
THIS FORMED A BRAND NEW
COMPOUND, NaCl IN WHICH BOTH
ELEMENTS WERE MORE STABLE, BUT
NOW HAVE A CHARGE.
OPPOSITELY CHARGED IONS
ATTRACT EACH OTHER AND FORM
AN IONIC BOND THAT IS
ELECTRICALLY NEUTRAL.
LOOKING AT THE STRUCTURE OF SALT
SHOWS THAT THE ATTRACTION
BETWEEN IONS IS SO GREAT THAT
MANY SODIUM AND CHLORIDE IONS
BECOME INVOLVED
PROPERTIES OF IONIC
COMPOUNDS
Properties of Ionic
Compounds
CAN CONDUCT
ELECTRICITY
WHEN DISSOLVED
OR MELTED, THE
IONS CONDUCT
ELECTRICITY
IONS IN A SALT
PACK IN HIGHLY
FORM REPEATING
ORDERED
PATTERNS CALLED
ARRANGEMENTS
A CRYSTAL LATTICE
Dissociation of salt
2
PROPERTIES OF IONIC
COMPOUNDS
HARD
PACKED INTO LAYERS,
TAKES A LOT OF
ENERGY TO BREAK ALL
OF THE BONDS
BRITTLE
IF A FORCE IS STRONG
ENOUGH TO REPOSITION A LAYER THEN
THE REPULSIVE FORCES
DRIVE IONS APART
PREDICTING THE FORMATION OF
IONIC COMPOUNDS
We can predict the combinations
of ions and the formation of their
ionic formulas by knowing how
the ions interact.
There are 2 different kinds of ionic
compounds
BINARY(2 elements metal + nonmetal)
and POLYATOMIC (metal + ion made up
PROPERTIES OF IONIC
COMPOUNDS
HIGH MELTING
POINTS AND
BOILING
POINTS
BECAUSE OF
STRONG
ATTRACTION
BETWEEN IONS, IT
TAKES A LOT OF
ENERGY TO BREAK
IONS APART
WRITING IONIC
FORMULAS
THERE ARE A COUPLE OF RULES
TO FOLLOW TO MAKE SURE THAT
THE PROPER IONIC FORMULA IS
WRITTEN.
of more than 2 elements)
RULE #1
IONS WILL COMBINE IN SMALL
WHOLE NUMBER RATIOS THAT
ADD TO GIVE A NEUTRAL
COMPOUND.
THE IONS’ CHARGES MUST
ADD UP TO ZERO
RULE #2
IT’S BETTER TO BE POSITIVE
THAN NEGATIVE
THE POSITIVE ION IS
ALWAYS WRITTEN FIRST.
3
Ionic compounds that gain or
lose the same number of
electrons automatically
combine in 1:1 ratios
How could we balance the
charge and form a compound?
WHAT IF WE WERE FORMING
IONIC COMPOUNDS WITH
IONS WHOSE CHARGES
DIDN’T ADD UP TO A CHARGE
OF EXACTLY 0?
HOW DO WE
DECIDE THE RATIO
OF THE IONS?
We need to find the ratio
of ions that will make the charges
cancel out to a neutral
compound.
CRISS-CROSS RULE:
WE HAVE A TRICK THAT WILL
HELP US KNOW THE NUMBER
OF THE IONS TO MAKE A
NEUTRAL COMPOUND.
IT’S NOT A TRICK SO MUCH
AS A SHORTCUT!
Step 1: Write the symbols for each element in the compound (metal element first).
Ca P
4
CRISS-CROSS RULE:
Step 2: Write the ionic charge as a superscript above each symbol. (eg. Al 3+)
.
2+
Ca P
3-
CRISS-CROSS RULE:
Step 3: Criss‐cross the numerals of the ionic charges and drop them as a subscript to determine the number of each element needed to balance the ionic charges.
2+ 3-
Ca P
CRISS-CROSS RULE:
CRISS-CROSS RULE
notes:
Step 4: Write the formula using subscripts for each element. •The subscript ‘one’ can be dropped.
•If both elements have the same subscript, the numbers can be dropped
•Subscripts must be reduced to lowest terms since the subscripts indicate the smallest whole number ratio of elements in the compound.
Ca 3 P 2
Calcium Phosphide
CRISS-CROSS RULE:
Nomenclature
5
Naming Ionic Compounds
• The name of the
metal goes first
• The name of the
non-metal is
second
• Take the “ine”
ending of the
element off and
replace with “ide”
• eg.
• AlCl3
• Elements:
Aluminum &
Chlorine
• Name:
Aluminum
Chloride
Nonmetals and their names
Group 15
Group 14
C4-,carbide
N3-, nitride
Group 16
Group 17
O2-, oxide
F-, fluoride
S2-, sulfide
Cl-, chloride
Br-, bromide
I-, iodide
54
NAMES OF NEGATIVE IONS
PARENT ELEMENT
NEGATIVE ION
CHLORINE
CHLORIDE
OXYGEN
OXIDE
NITROGEN
NITRIDE
PHOSPHORUS
PHOSPHIDE
FLUORINE
FLUORIDE
IODINE
IODIDE
SULFUR
SULFIDE
BROMINE
BROMIDE
NAMING
CaCl2  Calcium chloride
K3P  Potassium phosphide
Al2S3  Aluminum sulfide
METALS WITH MULTIPLE
CHARGES
Multivalent Metals
SOME METALS HAVE MORE THAN
ONE IONIC CHARGE
1) Figure out which charge the
metal has in the compound
2) Designate that metal with a
ROMAN NUMERAL between the
name of the metal and the nonmetal
Metal
Charge
Name
Charge
Name
Iron
2+
Iron (II)
3+
Iron (III)
Copper
1+
Copper (I)
2+
Copper (II)
Chromium
2+
Chromium (II)
3+
Chromium (III)
Manganese
2+
Manganese (II)
3+
Manganese (III)
Mercury
1+
Mercury (I)
2+
Mercury (II)
Tin
2+
Tin (II)
4+
Tin (IV)
Lead
2+
Lead (II)
4+
Lead (IV)
6
To name them, do the criss-cross
rule BACKWARDS
FeCl2  Iron(II) chloride
FeCl3  Iron (III) chloride
PbBr2  Lead (II) bromide
Write the formulas for these
 Lithium
sulfide
 Tin (II) oxide
 Tin (IV) oxide
 Magnesium fluoride
 Copper (II) sulfide
 Iron (III) phosphide
 Gallium nitride
 Iron (III)oxide
 Li2S
 SnO
 SnO2
 MgF2
 CuS
 FeP
 GaN
 Fe2O3
POLYATOMIC IONS
These are ions that contain several
Elements that are covalently
bound to each other.
Polyatomic ions don’t come
apart!!!
7