CHEMISTRY LAB C

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CHEMISTRY LAB C

• Team of 2 students
• 50 minutes
• Safety RequirementsWear apron or lab coatOSHA
  approved goggles with indirect vents
• Do not bring reference material or calculators

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CHEMISTRY LAB C

• A series of stations with various
  activitiesCould Include
• Hands-on Activities Experiments
• Interpretation of Experimental Data
• (graphs, charts, diagrams, data tables, etc.)
• Observation of Running Demonstration
• Redox Reactions Periodicity

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Periodicity

• Understand the periodic nature of the elements
• Demonstrated ConceptuallyPredicting and
  explaining trends
• Demonstrated ExperimentallyCollecting and/or
  accounting for data

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Topics Covered

• Physical Properties
• Electronic Structure and Bonding
• Chemical Properties

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Physical Properties

• Atomic and Ionic Radii
• Ionization Energy
• Melting Point
• Electronegativity

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Electronic Structure

• Electron Configuration
• Ionic and Covalent Bonding
• Charges on Ions
• Metallic Properties

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Chemical Properties

• Precipitation Formation
• (Solubility)
• Reaction with Acids
• Acidity of Oxides

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Dmitri Mendeleev

• Periodic Properties
• Arrange Elements According to Properties
• Families have similar properties
• All alkali metals react with water
• But to different degrees or reactivity
• Predict Ekasilicon between Si and Sn
• Later arranged according to atomic number not mass

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Electron Configuration - I

• H 1s 1
• He 1s 2
  He
• Li 1s2 2s 1
  He 2s 1
• Be 1s2 2s 2 He 2s 2
• B 1s2 2s 2 2p 1 He 2s 2 2p
  1
• C 1s 2 2s 2 2p 2 He 2s 2 2p
  2
• N 1s 2 2s 2 2p 3 He 2s 2 2p
  3
• O 1s 2 2s 2 2p 4 He 2s 2 2p
  4
• F 1s 2 2s 2 2p 5 He 2s 2
  2p 5
• Ne 1s 2 2s 2 2p 6 He 2s 2 2p6
  Ne

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Electron Configuration - II

• Na Ne 3s 1
• Mg Ne 3s 2
• Al Ne 3s 2 3p 1
• Si Ne 3s 2 3p 2
• P Ne 3s 2 3p 3
• S Ne 3s 2 3p 4
• Cl Ne 3s 2 3p 5
• Ar Ne 3s 2 3p6 Ar

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Order of Electron Filling
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Electron Configuration - III

• K Ar 4s 1
• Ca Ar 4s 2 Or this order
  is OK !
• Sc Ar 4s 2 3d 1
  Ar 3d 1 4s 2
• Ti Ar 4s 2 3d 2
  Ar 3d 2 4s 2
• V Ar 4s 2 3d 3
  Ar 3d 3 4s 2
• Cr Ar 4s 1 3d 5
• Mn Ar 4s 2 3d 5
• Fe Ar 4s 2 3d 6 Either order will
  be OK !
• Co Ar 4s 2 3d 7 But its normally
  best to
• Ni Ar 4s 2 3d 8 put the one filling
  last!!!
• Cu Ar 4s 1 3d 10
• Zn Ar 4s 2 3d 10

Anomalies to Filling
Anomalies to Filling
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Orbital Box Diagrams - III Na
Ar
Atomic Number Orbital Box
Condensed Electron Element
Diagrams(3s3p)
Configuration
11 Na
He 3s1 12
Mg
He 3s2 13 Al

He 3s23p1 14 Si

He 3s23p2 15 P

He 3s23p3 16 S

He 3s23p4 17 Cl

He 3s23p5 18 Ar

He 3s23p6
3s
3px
3py
3pz
3s
3px
3py
3pz
3s
3px
3py
3pz
3s
3py
3px
3pz
3s
3py
3px
3pz
3s
3py
3px
3pz
3py
3px
3pz
3s
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Orbital Box Diagram - IV Sc Zn
4s 3d
Z 21 Sc Ar 4s2 3d1
Z 22 Ti Ar 4s 2 3d 2
Z 23 V Ar 4s 2 3d 3
Z 24 Cr Ar 4s1 3d 5
Z 25 Mn Ar 4s 2 3d 5
Z 26 Fe Ar 4s 2 3d 6
Z 27 Co Ar 4s 2 3d 7
Z 28 Ni Ar 4s 2 3d 8
Z 29 Cu Ar 4s 1 3d 10
Z 30 Zn Ar 4s 2 3d 10
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Electronic Configuration Ions

• Na 1s 2 2s 2 2p 6 3s 1 Na 1s 2
  2s 2 2p 6
• Mg 1s 2 2s 2 2p 6 3s 2 Mg2 1s 2 2s
  2 2p6
• Al 1s 2 2s 2 2p 6 3s 2 3p 1 Al3 1s 2
  2s 2 2p 6
• O 1s 2 2s 2 2p 4 O- 2 1s
  2 2s 2 2p 6
• F 1s 2 2s 2 2p 5 F- 1
  1s 2 2s 2 2p 6
• N 1s 2 2s 2 2p 3
  N- 3 1s 2 2s 2 2p 6

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Fig. 8.23
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Atomic Size
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Atomic Size

• Across a rowDiameter Decreases Electrons added
  to the same shell More protons pull in electrons
  closer
• Down a columnDiameter Increases Electrons fill
  into further out shells

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Fig. 8.13
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Transition Metals

• Across the transition series (d block) the atomic
  radii initially decrease, then increase.
• Initially, the increase in the nuclear charge
  decreases the size when d electrons are added
  into a shell closer than the valence shell.
• Later the increased electron - electron repulsion
  from many electrons in the d orbitals cause the
  atomic radii to increase.

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Law of Dulong and Petit

• Heat Capacity is the amount of energy needed to
  raise the temperature of an amount of a substance
• 1819 Pierre Dulong and Alexis PetitProduct of
  molar mass and heat capacity is a constant for
  metals
• Heat capacity decreases with molar mass

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Ionization Energy

• The energy required to remove an electron from a
  neutral atom
• A energy ? A e-

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Second Ionization Energy

• The energy required to remove an electron from a
  1 cation
• A energy ? A2 e-
• Successive ionization energies are greater than
  earlier ionization energies

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Periodicity of First Ionization Energy (IE1)
Fig. 8.14
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Fig. 8.27
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Size of Ions

• Size of anions are larger than atomsAdding
  electrons to an atom increases the size Higher
  -/ ratio
• Size of cations are smaller than atomsRemoving
  electrons from an atom decreases the size Lower
  -/ ratio and often lose electrons in furthest
  shell

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Crystal Structures

• Ionic Crystals are lattice of large anions with
  smaller cations inbetween the anions
• (r / r-) gt 0.732 cations in cubic hole
• 0.732 gt (r / r-) gt 0.414 cations in
  octahedral holes
• 0.414 gt (r / r-) cations in tetrahedral holes

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Crystal Structures

• CsCl (r / r-) 0.169 nm/0.181nm gt 0.732
  cations in cubic hole BCC
• NaCl (r / r-) 0.095 nm/0.181nm 0.732 gt (r /
  r-) gt 0.414 cations in octahedral holes FCC
• ZnS (r / r-) 0.074 nm/0.184nm 0.414 gt (r /
  r-) cations in tetrahedral holes FCC

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Electron Affinity

• Energy released when an electron is added to a
  neutral atom
• A e- ? A- energy
• (Sometimes defined as energy needed to remove an
  electron from an anion)

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More Negative
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Trends in Three Atomic Properties
Fig 8.18
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Fig. 9.2
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Metals and Nonmetals

• MetalsShiny luster, various colors - mostly
  silverMalleable and ductileGood conductors of
  heat and electricityMost metal oxides are basic
  Na2O(s) H2O(l) gt 2 NaOH(aq)
  Generally form cations

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Metals and Nonmetals

• NonmetalsNo luster, various colorsUsually
  brittle - some hard, some softPoor conductors
  of heat and electricityMost nonmetallic
  compounds are acidicCO2(g) H2O(l) gt
  H2CO3(aq) Generally form anions or oxyanions

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Metalloids (Semimetals)

• Intermediate properties between metals and
  nonmetalsSome metallic characteristics and some
  nonmetal characteristicsSome, most notably Si,
  are electrical semiconductors

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Lattice Energy

• Li (g) F- (g) gt LiF (s)
• DHoLattice of LiF -1050 kJ

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Periodic Trends in Lattice Energy

• Electrostatic Force (C) (A-) / Distance
• Ionic Size
• Ionic Charge

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Melting and Boiling Points of Some Ionic
Compounds
Compound mp( oC)
bp( oC)
CsBr 636
1300 NaI
661
1304 MgCl2
714 1412 KBr
734
1435 CaCl2
782
gt1600 NaCl 801
1413 LiF
845
1676 KF
858
1505 MgO 2852
3600
Table 9.1 (p. 340)
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Electronegativity

• A scale to show the relative attraction of an
  atom for electrons shared in a bond
• Linus Pauling Scale
• Lowest Fr 0.7
• Highest F 4.0

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The Periodic Table of the Elements
2.1
He
0.9
1.5
2.0
2.5
3.0
3.5
4.0
Ne
Electronegativity
0.9
1.2
Ar
1.5
1.8
2.1
2.5
3.0
0.8
1.0
1.3
1.5
1.6
1.6
1.5
1.8
1.8
1.8
1.9
1.6
1.6
1.8
2.0
2.4
2.8
Kr
0.8
1.0
1.2
1.4
1.6
1.8
1.9
2.2
2.2
2.2
1.9
1.7
Xe
2.5
2.1
1.9
1.8
1.7
0.7
0.9
1.1
1.5
1.7
1.9
2.2
2.2
2.4
1.9
Rn
2.2
2.0
1.9
1.8
1.8
1.3
2.2
0.7
0.9
1.1
Ce Pr Nd Pm
Yb Lu
1.1
1.1
1.1
1.1
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.3
1.3
1.5
1.7
1.3
1.3
1.3
1.3 1.3
1.3
1.3
1.3
1.5
1.3
Th Pa U Np
No Lr
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Bond Polarity

• Nonpolar Covalent BondsElectronegativity
  Difference is ideally 0 Very small differences
  are still considered to be mostly covalent bonds,
  up to about 0.4
• Polar Covalent BondsElectronegativity
  Difference measurableHas polar covalent
  characteristics up to 2.0
• Mostly Ionic Bonds High Electronegativity
  Differences

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Bond Polarity

• Cl2 is a nonpolar covalent bond DE (3.0 - 3.0)
  0
• HCl is a polar covalent bond DE (3.0 - 2.1)
  0.9
• NaCl is a very polar bond - ionic DE (3.0 -
  0.9) 2.1

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The Redox Process in Compound Formation
Fig. 4.13
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Oxidation-Reduction Reactions

• How can we predict if a oxidation-reduction
  reaction will occur
• Experimental trials give reactivity relationships

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Metal Activity

• Higher activityMore the metal wants to be
  oxidizedMore the metal wants to gain
  electronsBetter reducing agent
• Compare to other metals
• Compare to H in water and acids

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Activity Series

• Mg gt Mg2 has a higher activity than
• Zn gt Zn2
• Therefore
• Mg Zn2 gt Mg2 Zn
• and
• Zn Mg2 gt No Reaction

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Activity Series

• Cr gt Cr3 has a higher activity than
• Ni gt Ni2
• Therefore
• 2Cr 3Ni2 gt 2Cr3 3Ni
• and
• Ni Cr3 gt No Reaction

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Basic and Acidic Oxides

• More ionic oxides formed on left side of periodic
  table
• If dissolve in water form basic solutionsMO(s)
  H2O(l) ? M2(aq) 2 OH-(aq)

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Basic and Acidic Oxides

• More covalent oxides formed on right side of
  periodic table
• If dissolve in water form acidic solutionsMO(g)
  H2O (l) ? H2MO2(aq)H2MO2(aq) H2O ?H3O(aq)
  HMO3-(aq)