I. Forming Chemical Bonds

Chapter 8 Ionic Compounds
I. Forming Chemical Bonds – How do
Compounds Form?
• Stability
• Compounds want to have a noble gas configuration (8
valence electrons)
I. Why do atoms form bonds?
Chemical Bond - strong attractive force
between atoms or ions in a compound.
•  stability - goal is to reach the most
energetically favorable condition
•  bond energy - energy involved in process of
bond forming or bond breaking
•  Valence Electrons outermost electrons
Highest Energy Level
Valence Electrons?
3s23p6
How do you represent Valence Electrons?
Electron Dot Structures
1.
What is the atomic number of this element?
2.
Write the electron configuration.
3.
Identify just the valence electrons (hint use the
“A” roman numerals on the periodic table).
How do you represent Valence Electrons? Electron Dot
Structures
4.
5.
Write the symbol for the element.
Use a dot for each valence electron. An
element with a complete valence shell (8 e-) will
look like this:
X
Try these examples:
Li
B
N
F
Be
C
O
Ne
1. shows valence electrons, for
example lets try these……
Li
B N
F
Valence
electron
C
O
Ne
Be
Stable Octet (new words, octet rule): 8
electrons in valence shell, stable
configuration
II. Ionic Bonding: process by which one
or more electrons are transferred from the
valence shell of one atom to the valence
shell of another atom. (usually forms
salts)
Unstable
3s1
3p5
3s2
Electons Transferred = ionic bond
Stable
11P+
10e1+charge
Electrostatic
attraction
full
octets
17P+
18e1- charge
Ionic Bonding
8.3. Names and Formulas for Ionic
Compounds (8.3 pgs. 221-227)
A. Formulas tell:
1. which elements make up the compound
(qualitative)
2. ratios of atoms contained (quantitative)
Hydrogen &
Oxygen in
element
H 2O
# of H’s
and O’s
in
molecule
B. Made from a metal + a nonmetal
1. metals form (+) ions - cations
2. nonmetals form (-) ions - anions
C. Using ion charge to write formulas
1. write the chemical symbol
2. using the periodic table assign a
charge
(to be written as a subscript)
Group
1+
IA,
2+
IIA,
3+
IIIA,
3VA,
2VI,
1VIIA
3. add charges together to equal
zero, use charge of one ion as
subscript for the other ion, or use
criss-cross method
4. when subscripts are equal they
reduce to 1
5. for polyatomics (more than one
atom combined that has an overall
charge), use parenthesis when
subscript is 2 or more
examples:
Calcium chloride
Ca2+ + Cl1- + Cl1- = 0
CaCl2
examples:
Calcium chloride
CaCl2
Aluminum oxide
Magnesium phosphate
Barium sulfate
Al2O3
Magnesium sulfide
MgS
Ammonium chloride
examples:
Magnesium phosphate
Mg32+ PO43-2
Mg3(PO4)2
examples:
Barium sulfate
BaSO4
Ammonium chloride
NH4Cl
D. Naming ionic compounds
1. binary compounds - two different
kinds of atoms
a. name the first element
b. name the second element,drop
the last syllable, add -ide.
examples:
Na2S = Sodium Sulfide
MgO = Magnesium Oxide
Naming ternary compounds
2. ternary compounds - name the first
element, then name the polyatomic ion
examples:
Ca(NO3)2 = Calcium Nitrate
Na2SO4 = Sodium Sulfate
E. atoms that form more than one type of
ion
(examples: Cu, Fe, Hg, Pb, Sn)
1. old system - call the ion with the
greater charge -ic, and the ion with the
lesser change -ous. (use Latin names
as roots)
Cu+1
Cu+2
Fe+2
Fe+3
cuprous
cupric
ferrous
ferric
CuF
CuF2
FeF2
FeF3
cuprous fluoride
cupric fluoride
ferrous fluoride
ferric fluoride
2. new system (or stock system), name
ion by atom. The name is followed
by roman numeral telling its charge.
Cu+1 copper(I)
`
CuF copper (I) fluoride
Cu+2 copper(II)
CuF2 copper (II) fluoride
Fe+2 Iron(II)
FeF2 iron (II) fluoride
Fe+3 Iron(III)
FeF3 iron (III) fluoride
III. Properties of Ionic Compounds:
Crystal Lattice- three dimensional
arrangement of cations & anions
List Properties here
•  Crystal shape
•  Hard & brittle
•  High melting pt
•  High boiling pt
•  When dissolved,
or molten, conducts
electricity
Properties of Ionic Solids
Electrons transferred = ionic bond
Electrostatic Attraction
Crystal shape
Unit cell – simplest, repeating unit
IV. Energy and the Ionic Bond:
• During any chemical or physical reaction
energy is neither created or destroyed
• Energy that is absorbed is called endothermic
• Energy that is release is called exothermic
• The formation of ionic compounds from
positive and negative ions is always exothermic.
The compound formed is more stable and of
lower energy.
IV. Energy and the Ionic Bond:
• The energy required to separate one mole of the
ions of an ionic compound is referred to as the
lattice energy.
• The more negative the lattice energy, the stronger
the force of attraction.
• Which would have more negative lattice energy,
lithium chloride or lithium bromide?
Lithium chloride
• MgO is almost four times greater then the lattice
energy of NaF, why?
MgO, charge of the ions is greater
V. Names and Formulas for Ionic
Compounds(8.3 pgs. 221-227)(see previous notes)
!Describe a Pot of Gold (physical and
chemical properties of the pot and the
gold coins)
High luster
High Melting/Boiling Pt.
Malleable
Ductile
Solid
Conductive
VI. Metallic Bonds and Properties of
Metals (8.4 pgs. 228-231)
1.  Metals form a lattice with eight to 12
other metal atoms surrounding each
metal atom.
2.  metals have at least one valence electron,
they do not form ions or share their
electrons
3.  metals are crowded with electrons and
the outer energy levels of the metal
atoms overlap
VI. Metallic Bonds and Properties of
Metals (8.4 pgs. 228-231)
4.  The electron sea
model proposed
that all the metal
atoms in a
metallic solid
contribute their
valence electrons
dot form a “sea”
of electrons.
5.  Electrons are not held tightly by any
specific atom, electron are free to move
around and are referred to delocalized
electrons.
6.  The attraction of a metallic cation for
delocalized electrons is called a metallic
bond.
Properties of Metallic
Bonding