Transcript 4.IonicCompounds - Gleneaglesunit1and2chemistry2012

Octet Rule = atoms tend to gain, lose or share electrons so
as to have 8 electrons
C would like to Gain 4 electrons
N would like to Gain 3 electrons
O would like to Gain 2 electrons
Electron Dot Structures
Symbols of atoms with dots to represent the valence-shell
electrons
1
2
13
14
15
16
17
H
18
He:

Li Be


B 


C


Na Mg


Al

N



O




 Si 
P
 S





: F  :Ne :




:Cl  :Ar :


Chemical bond
• A chemical bond forms when outer-shell
electrons of different atoms come close
enough to each other to interact and
rearrange themselves into a more stable
arrangement.
Types of Chemical Bonds
• Ionic bonds formed when metal atoms
combined with non-metal atoms
• Metallic bonds formed when metal atoms
combined with metal atoms.
• Covalent bonds formed when non-metal
atoms combined with non-metal atoms.
Ionic Compounds
1). Ionic bond – electron from Na is transferred to Cl,
this causes a charge imbalance in each atom. The Na
becomes (Na+) and the Cl becomes (Cl-), charged
particles or ions.
The coordination number of an
ionic lattice is written
as a ratio x:y
How many chlorine ions surround
each sodium ion and vice versa?
NaCl coordination number- 6:6
Hardness and Brittleness
 Figure 6.4 The repulsion
between like charges
causes this sodium
chloride crystal to
shatter when it is hit
sharply.
Electrical Conductivity
• In the solid form, ions in sodium chloride are held
in the crystal lattice and are not free to move so
cannot conduct electricity.
• When the solid melts the ions are free to move.
• In a similar way, when sodium chloride dissolves
in water, the ions separate and are free to move
towards the opposite charge.
Properties of Ionic Compounds
– Forms crystal composed of 3d array of ions (ionic
network lattice)
– Have high melting and boiling temperatures.
– Are hard but brittle
– Do NOT conduct electricity in the solid state
– They will only conduct electricity if they are melted or
dissolved in water.
Structure
• From the properties we can conclude:
– The forces between the particles are strong.
– There are no free-moving electrons present,
unlike in metals.
– There are charged particles present, but in solid
state they are not free to move.
– When an ionic compound melts, however, the
particles are free to move and the compound
will conduct electricity.
Use Electron shell diagram and simple equation to
show the formation of:
• NaCl
• MgO
Naming Binary Ionic Compounds
Contain 2 different elements
 Name the metal first, then the nonmetal as -ide.
NaCl
ZnI2
Al2O3
Examples:
sodium chloride
zinc iodide
aluminum oxide
Practise
Complete the names of the following binary
compounds:
Na3N
________________
KBr
________________
Al2O3
________________
MgS
_________________________
Solution
Complete the names of the following binary
compounds:
Na3N
sodium nitride
KBr
potassium bromide
Al2O3
aluminum oxide
MgS
magnesium sulfide
Transition Metals
Many form 2 or more positive ions
1+
2+
1+ or 2+
2+ or 3+
Ag+
Cd2+
Cu+, Cu2+
Fe2+, Fe3+
silver
ion
cadmium
ion
Zn2+
zinc ion
copper(I) ion
iron(II) ion
copper (II) ion iron(III) ion
Write symbols for these:
• Potassium ion
• Magnesium ion
• Copper (II) ion
• Chromium (VI) ion
• Barium ion
• Mercury (II) ion
Formula of ionic compounds
Criss-Cross Method
1. Write the symbols for the ions side by side. Write the
cation first.
• Al3+ O22. Cross over the charges by using the absolute value of each
ion’s charge as the subscript for the other ion.
• Al2
O3
3. Check the subscripts and divide them by their largest
common factor to give the smallest possible whole-number
ratio of ions. Then write the formula.
• Al2O3
•
For Al: 2 x 3+ = 6+
For O: 3 x 2- = 6-
Criss-Cross Method
Example 1: Calcium and Oxygen
Calcium
Ca2+
Oxide
O2-
Ca2+
O2Ca2O2
CaO
Criss-Cross Method
Example 2: Magnesium and Phosphorus
Magnesium
Mg2+
Phosphorus
P3-
Mg2+
P3-
Mg3P2
The sum of the cation charge and the sum of the anion charge
must cancel each other so that the compound formed is
neutral.
Practise
1. The formula for the ionic compound of
Na+ and O2- is
1) NaO
2) Na2O
3) NaO2
2. The formula of a compound of aluminum and
chlorine is
1) Al3Cl
2) AlCl2
3) AlCl3
3. The formula of Fe3+ and O2- is
1) Fe3O2
2) FeO3
3) Fe2O3
Solution
A. The formula for the ionic compound of
Na+ and O2- is
2) Na2O
B. The formula of a compound of aluminum and
chlorine is
3) AlCl3
C. The formula of Fe3+ and O2- is
3) Fe2O3
Sample Problem 7-1
•Write the formulas for the binary ionic compounds
formed between the following elements:
A. lithium and fluorine
B. lithium and oxygen
Names of Variable Ions
Use a roman number after the name of a metal
that forms two or more ions
Transition metals and
the metals in groups 4A and 5A
FeCl3
(Fe3+)
iron (III) chloride
CuCl
SnF4
PbCl2
Fe2S3
(Cu+ )
(Sn4+)
(Pb2+)
(Fe3+)
copper (I) chloride
tin (IV) fluoride
lead (II) chloride
iron (III) sulfide
II. Stock system (roman numerals)
Example:
Fe2+
Fe3+
• Iron(II)
• Iron(III)
CuCl
• copper(I) chloride
CuCl2
• copper(II) chloride
Sample Problem 7-2
a. Write the formula and give the name for the
compound formed from the ions Cr3+ and F-.
b. Write the name for Cu3N2.
Here are the changes in the electronic structure of iron to make the 2+ or the 3+ ion.
Fe
[Ar] 3d64s2
Fe2+
[Ar] 3d6
Fe3+
[Ar] 3d5
Learning Check
Complete the names of the following binary
compounds with variable metal ions:
FeBr2
iron (_____) bromide
Cu2O
copper (_____) oxide
SnCl4
___(_____ ) ______________
Fe2O3
________________________
CuS
________________________
Solution
Complete the names of the following binary
compounds with variable metal ions:
FeBr2
iron ( II ) bromide
Cu2O
copper ( I ) oxide
SnCl4
tin (IV) chloride
Fe2O3
iron (III) oxide
CuS
copper (II) sulfide
Learning Check
Name the following compounds:
A.
CaO
1) calcium oxide
2) calcium(I) oxide
3) calcium (II) oxide
B.
SnCl4
1) tin tetrachloride
3) tin(IV) chloride
C. Co2O3
1) cobalt oxide
3) cobalt trioxide
2) tin(II) chloride
2) cobalt (III) oxide
Solution
Name the following compounds:
A.
CaO
1) calcium oxide
B.
SnCl4
3) tin(IV) chloride
C.
Co2O3
2) cobalt (III) oxide
Learning Check
Write the correct formula for the compounds
containing the following ions:
A. Na+, S21) NaS
2) Na2S
3) NaS2
B. Al3+, Cl1) AlCl3
2) AlCl
3) Al3Cl
C. Mg2+, N31) MgN
2) Mg2N3
3) Mg3N2
Solution
A. Na+, S22) Na2S
B. Al3+, Cl1) AlCl3
C. Mg2+, N33) Mg3N2
Practise
Name the following ionic compounds:
Na2O
K2S
CaCl2
AgCl
MgBr2
AlN
Ba3As2
AlH3
ZnI2
Li3P
Nomenclature of binary ionic compounds
Answers:
Na2O = sodium oxide
K2S = potassium sulfide
MgBr2 = magnesium bromide
AlN = aluminum nitride
Ba3As2 = barium arsenide
CaCl2 =
AgCl = silver chloride
AlH3 = aluminum hydride
ZnI2 = zinc iodide
phosphide
calcium chloride
Li3P = lithium
III. Polyatomic Ions
A charged group of covalently bonded
atoms
Combine with ions of opposite charge to form
ionic compounds
Ex: NH4+, NO3-, SO42-
Nomenclature of binary ionic compounds
Some polyatomic anions that you must know:
NO3- = nitrate
NO2- = nitrite
SO4 2 - = sulfate
SO32- = sulfite
PO43- = phosphate
PO33- = phosphite
CO32- = carbonate
HCO31- = hydrogen carbonate or bicarbonate
OH- = hydroxide
CN- = cyanide
C2H3O2- = acetate
C2O42- = oxalate
III. Polyatomic Ions
Most common ion is given the ending –ate.
• One less oxygen than –ate ends in –ite.
• One less oxygen than –ite is given the prefix hypo.
• One more oxygen than -ate is given the prefix per.
ClO4
• perchlorate
ClO3
• chlorate
NO3
• nitrate
ClO2
• chlorite
NO2
• nitrite
ClO
• hypochlorite
Sample Problem 7-3
a. Write the formula for potassium sulfate.
b. Write the formula for calcium carbonate.
c. Write the formula for tin(IV) sulfate.
Ionic Nomenclature Practice
potassium chloride

K+ Clmagnesium nitrate
KCl
Mg2+ NO3
copper(II) chloride
Mg(NO3)2
Cu2+ Cl-

CuCl2
Nomenclature of binary ionic compounds
Naming salts composed of the polyatomic ions is the
same as with the monatomic anions. Metal name then
polyatomic name.
NaOH sodium hydroxide
H2SO4 hydrogen sulfate
Ba(NO3)2 barium nitrate
CsNO2
cesium nitrite
Sometimes there is a common name:
KHCO3 potassium hydrogen carbonate or potassium bicarbonate
Note: the polyatomic anions must be memorized.
Name the following ionic compounds:
NaHCO3
K2SO3
MgSO4
Ca(OH)2
NH4NO3
Zn(NO3)2
KCN
Li3PO4
H2PO4
HNO3