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Ch 5
Ions and ionic cpds
Chemical reactivity:
Depends on electron configuration, noble
gas least reactive (s&p filled)
Octet rule: atoms tend to react to fill s&p
valence electron shells.
Chemical reactivity
Alkali metals and halogens most
reactive elements
 Atoms lose, gain or share electrons to
obtain an octet.
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Alkali metals: ns1 configuration -> lose one
electron (1+ change)
 Halogens: ns2p5 configuration -> gain one
electron (1- change)
 Both reach an octet, filled s & p valence
shell.
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Valence electrons
Use electron configuration to determine # of
valence electrons . Look for highest PQ# s & p
electrons.
 Gain or lose electrons --> stable ion
 Lose electrons --> cation (+) charge = #
electrons lost
 Gain electrons --> anion (-) charge = #
electrons gained
 Both cases reach an octet.
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Characteristics of stable ions
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Filled s&p orbits of highest energy level
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Noble gas configuration, octet
Ions have electric charge
 Combine cation w/ anion in cpd
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Conduct electric current in water
Transition metals ions w/out complete octet
Have multi oxidation states
 All cations.
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Atoms and ions
Different chemical properties.
 Metals --> cations, less energy to lose
electrons (1 to 3) than to gain (5 to 7)
 Nonmetals --> anions, less energy to gain
electrons (1 to 3) than lose (5 to 7)
 Cations and anions combine to form
compounds with very specific properties
separate from the metals and nonmetals
properties.
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Ionic bonding and salts
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Ionic bond: electrostatic attraction between opposite
charges of cations and anions.
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Salt: ionic cpd that forms when a metal atom or a
positive radical replaces the hydrogen of an acid
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Forms solids called salts.
Electrically neutral
Simple whole number ratio based on charge of ions
Distinctive crystal structure
Transferring electrons involve D energy. Overall
energy D is exothermic.
Na + E --> Na+ + e-
Cl + e- --> Cl- + E
Salt formation (pg 169 figure 9)
Endothermic (breaking bonds)
 1. Na(s) + E --> Na(g) sublimation
 2. Na(g) + E --> Na+ + e- ionization E
 3. Cl-Cl + E --> 2Cl(g) bond E
 Exothermic (bond forming)
 4. Cl(g)+ e- --> Cl-(g) + E electron affinity
 5. Na+ (g) + Cl-(g) --> NaCl(s) + E lattice E
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Lattice energy
Energy associated with constructing a
crystal lattice relative to the energy of all
constituted atoms
 Energy released w/ crystal structure of a
salt as formed, key to salt formation.
 Net energy is exothermic:
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Energy to separate ions in water is
supplied by water.
 If a salt is not soluble, water does not have
enough E to break ionic bonds
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Ionic cpds
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Minerals of earth’s crust, cations + anion --> salt
Do not consist of molecules
ionic bonds are strong, attraction between opposite
charges.
Distinctive properties (pg 171 table 1)
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High boiling and melting pts
Solids at room temperature
Conduct electric current (l) or (aq)
Hard and brittle, ions arranged in repeating patterns,
layers.--> shatter along cleavage plane.
Salt crystals
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Form repeating patterns --> crystal lattice
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Repeating units, reason for crystal shape
Crystal structure depends on size & ratio on
ions (pg 174 figure 12)
 Salts have ordered packing arrangement
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Until cell: smallest repeating unit in a crystal
lattice.
 Determined by x-ray diffraction crystallography.
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Make model of arrangement of unit cells
based on diffraction patterns.
Names and formulas of ionic cpds
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Naming ionic cpds:
Binary salts (2 elements, metal/nonmetal ions)
Cation: name metal, roman numeral if multi oxidation
state.
Anion: root word of nonmetal and end in ide.
Writing ionic formulas:
Total positive charge = total negative charge. Net
charge of cpd = 0
1. Write symbol & charge of cation & anion
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Multiple oxidation state metals-> use roman numeral to
indicate charge. (I) (II) (III) (IV) (V) (VI)
2. Reduce if possible
3. Cross over just the number --> subscripts.
Practice
Write the formula for the following:
 Copper (II) oxide, sodium fluoride, zinc
chloride, aluminum sulfide, chromium (VI)
oxide.
 Name the following:
 Ca3N2, FeI3, Na2O, AlCl3, SrO, MnO2
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Polyatomic ions
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Ion made of two or more atoms covalently bonded
with a net positive or negative charge (pg 178
table 2)
Form ionic bonds with opposite charged ions.
Naming polyatomic ions:
Oxypolyatomic ions
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End in ite or ate as determined by # of oxygen's (SO3 2sulfite, SO4 2- sulfate)
With addition of hydrogen atom (HPO4 2- monohydrogen
phosphate)
Thio means replace oxygen with sulfur (S2O3 2thiosulfate)
Naming or writing formula with polyatomic ion
same as before. Use polyatomic name as is.
Practice
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Write the formula for the following:
Aluminum nitrate, magnesium phosphate,
ammonium acetate, iron (II) thiosulfate, Copper
(I) peroxide.
Name the following:
Ca(NO3)2, CuSO4, CuNO3, Na2CO3, K2Cr2O7