Section 7.3
Names and Formulas
For
Ionic Compounds
Naming Compounds
Name of a student _________ _________
first
last
Name of an ionic compound
sodium chloride
Which substance lost electrons?
Which substance gained electrons?
Formula Unit
Chemical compound of an ionic compound
Simplest ration of the ions involved
Magnesium Chloride
Magnesium group 2 Mg2+
Chlorine group 17 ClWant net charge of zero:
Have 2+ and 1Want 2+ and 2- so need 2 ClRatio 1:2
MgCl2
Ratios
Determine the ratio from the formula units
Ag2S
MgCl2
Al2O3
On Your Own
Determine the ratio
SnF4
FeO
Monatomic Ions
One-atom ion
Mg2+
BrUse the periodic table.
What is the formula for beryllium ion?
Iodide ion?
Nitride ion?
Common Monatomic Ions
Group
Atoms
1
15
H, Li, Na, K,
1+
Rb, Cs
Be, Mg, Ca, Sr, 2+
Ba
N, P, As
3-
16
O, S, Se, Te
2-
17
F, Cl, Br, I
1-
2
Charge on Ions
Monatomic Metal Ions
Group
Common Ions
3
Sc3+, Y3+, La3+
4
Ti2+, Ti3+
5
V2+, V3+
6
Cr2+, Cr3+
7
Mn2+, Mn3+, Tc2+
8
Fe2+, Fe3+
Continued
Group
Common Ions
9
Co2+, Co 3+
10
Ni2+, Pd2+, Pt2+, Pt 4+
11
Cu+, Cu2+, Ag+, Au+, Au 3+
12
Zn2+, Cd2+, Hg2+
13
Al 3+, Ga2+, Ga 3+, In+,In2+, In 3+, Tl+, Tl 3+
14
Sn2+, Sn 4+, Pb2+, Pb 4+
Oxidation Numbers
The charge on a monatomic ion
Oxidation number or oxidation state
Equals the number of electrons transferred
from the atom to form the ion
Notice some ions have more than one
oxidation state – with the d orbital
elements
Binary Ionic Compounds
Symbol Cation then Anion
Subscripts equals number of ions
if no subscript then it is 1
How to figure the Formula
Write the symbol and charge for each ion
Find the ratio of ions in the formula
• Overall charge must be zero
• Subscripts times the charges sum to zero
Example 7.1
Determine the formula for the ionic compound
formed from potassium and oxygen.
Potassium group 1 K+
Oxygen group 16 O2Ratio: 2:1
K2O
Evaluate: 2 K ions (+1) + 1 O ion (-2)
= 2 (+1) + 1(-2) = 2 + (-2) = 0
Example 7.2
Determine the formula for the compound formed
from aluminum ions and sulfide ions.
Aluminum group 13 Al3+
Sulfur group 16 S2Ratio: 2:3
Al2S3
Evaluate: 2 Al ions (3) + 3 S ions (-2)
= 2 (3) + 3 (-2) = 6 + (-6) = 0
Practice
Write the ionic compound formula.
19. Potassium and
iodide
20. Magnesium and
chloride
21. Aluminum and
bromide
22. Cesium and nitride
19. KI
20. MgCl2
21. AlBr2
22. Cs3N
Polyatomic Ionic Compounds
Ionic compounds made from more than one
atom.
Popular ions
Ammonium NH4+
Nitrite NO2Nitrate NO3Hydroxide OHCyanide CN-
Formulas for Polyatomic Ionic
Compounds
Mg(NO3)2
Mg2+ + (NO3)-
Al(NO3)3
Al3+ + (NO3)-
ratio 1:2
ratio 1:3
Use parenthesis to surround the polyatomic
ion
Practice
Write the formula for
ionic compounds.
24. Sodium and nitrate
25. Calcium and
chlorate
26. Aluminum and
carbonate
24. Ratio 1:1
Na+ + (NO3)- Na(NO3)
25. Ratio 1:2
Ca2+ + (ClO3)- Ca(ClO3)2
26. Ratio 2:3
Al3++(CO3)2- Al2(CO3)3
Naming Ionic Compounds
1. Name the cation followed by the anion
2. For monatomic cations use the element
name
3. For monatomic anions change the suffix
to –ide.
Rule 1
CsBr
Cesium Bromide
Rule 2
Rule 3
4. To distinguish between multiple oxidation
numbers of the same element use (roman
numerals) after the symbol.
Fe2+ + O2-  FeO Iron (II) Oxide
Fe3+ + O2-  Fe2O3 Iron (III) Oxide
5. When the compound contains a
polyatomic ions use the polyatomic ion
name.
NaOH is sodium hydroxide
(OH)-
(NH4)2S is ammonium sulfide (NH4)+
Naming Ionic Compounds
Determine the
cation and anion
of the given formula
Does the cation have
only one oxidation
number?
Yes
Write the name of
the cation, then the
name of the anion
No
Wite the name of the
the cation followed
by a Roman numeral to
represent the charge, then
write the anion name.
Practice Problems
Name the following compounds.
28. NaBr
29. CaCl2
30. KOH
31. Cu(NO3)2
32. Ag2CrO4
Each Student
Make a 5 x 5 chart
Across the top write 5 non-metal ions, with
one polyatomic anion
Along the side list 5 metals, with ammonium
ion.
Trade charts with another student, name
each compound in the boxes.
Trade back and check.
Summary
A formula unit gives the ratio of cations to
anions in the ionic compound.
A monatomic ion is formed from one atom.
The charge of amonatomic ion is its
oxidation number.
Roman numerals indicate the oxidation
number of cations having multiple possible
oxidation states.
Polyatomic ions consist of more then one
atom and act as a single unit.
To indicate more than one polyatomic ion in
a chemical formula, place parentheses
around the polyatomic ion and use a
subscript.
Practice Problems
34. State the order in which the ions
associated with a compound composed
of potassium and bromine would be
written in the chemical formula and the
compound name.
35. Describe the difference between a
monatomic ion and a polyatomic ion, and
give an example of each.
36. Ion X has a charge of 2+ and ion Y has
a charge of 1-. Write the formula unit of
the compound formed from the ions.
37. State the name and formula for the
compound formed from Mg and Cl.
38. Write the name and formula for the
compound formed from sodium ions and
nitrite ions.
Exit Ticket
This is the formula for making artificial ocean
water often used in saltwater aquariums.
Mix 24.72g NaCl, 0.67g KCl, 1.36g CaCl,
4.66g MgCl2, 6.29g MgSO4 and 0.18g
NaHCO3.
Name each ionic compound.