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Chapter 8 Ionic Compounds
I. Forming Chemical Bonds – How do Compounds Form?
•Stability
•Like the noble gases, every element wants to be inert
•Not a nerd
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
3s23p6
Valence Electrons?
Highest Energy Level
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. Write the symbol for the element.
5. Use a dot for each valence electron. s
orbitals on one side p orbitals on remaining
three sides of element.
Try these examples:
Li B N F Be C O Ne
1. shows valence electrons, for example lets try these……
Li B N F Be
C O Ne
Valence
electron
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
Stable
3s1
3s2
3p5
full
octets
11P+
10e-
1+charge
17P+
18e-
1- charge
Electons Transferred = ionic bond
Electrostatic
attraction
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)
H2O
Hydrogen & Oxygen in element
# 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) 1+ 2+ 3+ 3- 2- 1-
Group IA, IIA, IIIA, VA, VI, VIIA
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 Magnesium phosphate
Aluminum oxide Barium sulfate
Magnesium sulfide Ammonium chloride
CaCl2
Al2O3
MgS
examples:
Magnesium phosphate
Mg2+ PO4
3-
Mg3(PO4)2
2 3
examples:
Barium sulfate
Ammonium chloride
BaSO4
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 =
MgO =
Sodium Sulfide
Magnesium Oxide
Naming ternary compounds
2. ternary compounds - name the first element, then name the polyatomic ion
examples:
Ca(NO3)2 =
Na2SO4 =
Calcium Nitrate
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 cuprous CuF cuprous fluoride
Cu+2 cupric CuF2 cupric fluoride
Fe+2 ferrous FeF2 ferrous fluoride
Fe+3 ferric FeF3 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
Crystal Lattice- three dimensional arrangement of cations & anions
• Crystal shape
• Hard & brittle
• High melting pt
• High boiling pt
• When dissolved,
or molten, conducts
electricity
III. Properties of Ionic Compounds:
List Properties here
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
III. How do you name Salts?
A. Formulas tell: 1. which elements make up the compound (qualitative) 2. ratios of atoms contained (quantitative) H2O
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)
+1 +2 +3 -3 -2 -1
Group IA, IIA, IIIA, VA, VI, VIIA
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 Magnesium phosphate
Aluminum oxide Barium sulfate
Magnesium sulfide Ammonium chloride
CaCl2
Al2O3
MgSO4
Mg3(PO4)2
BaSO4
NH4Cl
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