Transp10312011 page 1
IONIC COMPOUNDS
The Octet Rule can be used to
predict stable:
a)cations for metals
(ex. K loses 1 e to make K+)
b)anions for nonmetals
(ex. Br gains 1 e to make Br- )
For each atom and ion you should be able to write:
1)electron configurations
2)orbital diagrams
3)electron dot structures
Can YOU do this?
Chemical Bond: force holding atoms together.
Ionic Bond: + charge on cation
& – charge on anion provide
attractive force between pairs
of these ions
Ex. Table Salt Na+ attracts Cl-
however,
There is not an NaCl molecule.
Instead there’s an ionic lattice:
see p 217
Formula Unit: gives the simplest ratio between cations and anions in the ionic compound.
ex. for sodium chloride the ratio is
Na: Cl = 1:1
(there’s one Na+ for each Cl-)
The formula for sodium chloride is
NaCl
What’s the formula for magnesium bromide?
Cation: Mg2+ Anion: Br-
The 2e’s lost by one Mg
form 2 Br- ions.
What’s the resulting formula?
Practice: Use the Principle of ChargeBalance (Total charge of ions in the formula of an ionic compound must be zero) to determine the formula when the given metal & nonmetal react to form an ionic compound in each of the following.
a)magnesium and oxygen
b)sodium and oxygen
c)aluminum and fluorine
d)aluminum and sulfur
NAMING IONIC COMPOUNDS
Binary Compound – composed of positively charged monatomic ions of a metal and negatively charged monatomic ions of a nonmetal.
In binary compounds of the representative elements:
Metal Cation has name of metal
and
Nonmetal Anion has “–ide” suffix.
Ex. Na+ is “sodium” in compd name
Cl- is “chloride” in compd name
Al3+ is “aluminum”
O2- is “oxide” etc.
Naming a Binary Compound
First Name Last Name
Metal Ion Nonmetal Ion
Ex. KBr is potassium bromide
Na2S is sodium sulfide
AlCl3 is aluminum chloride
What is the name of these?
a. CaO b. CaBr2 c. Al2O3
d. Li2O e. Na3N