Post on 28-Dec-2015
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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
CHEMISTRY LAB C
• A series of stations with various activitiesCould Include:
Hands-on Activities: ExperimentsInterpretation of Experimental Data
– (graphs, charts, diagrams, data tables, etc.)
Observation of Running Demonstration
Redox Reactions & Periodicity
Periodicity
• Understand the periodic nature of the elements
Demonstrated ConceptuallyPredicting and explaining trends
Demonstrated ExperimentallyCollecting and/or accounting for data
Electronic Structure
Electron Configuration
Ionic and Covalent Bonding
Charges on Ions
Metallic Properties
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
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]
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]
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 it’s 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
Orbital Box Diagrams - III Na ArAtomic Number Orbital Box Condensed Electron Element Diagrams(3s&3p) 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
3s
3s
3s
3s
3s
3s
3px
3px
3px
3py
3py
3py
3py
3py
3py
3py
3px
3px
3px
3px
3pz
3pz
3pz
3pz
3pz
3pz
3pz
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
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 Mg+2 1s 2 2s 2 2p6
• Al 1s 2 2s 2 2p 6 3s 2 3p 1 Al+3 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
Atomic Size
• Across a rowDiameter Decreases
Electrons added to the same shellMore protons pull in electrons closer
• Down a columnDiameter Increases
Electrons fill into further out shells
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.
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
Ionization Energy
• The energy required to remove an electron from a neutral atom
A + energy A+ + e-
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
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
Crystal Structures
• Ionic Crystals are lattice of large anions with smaller cations inbetween the anions
• (r+ / r-) > 0.732 cations in cubic hole
• 0.732 > (r+ / r-) > 0.414 cations in octahedral holes
• 0.414 > (r+ / r-) cations in tetrahedral holes
Crystal Structures
• CsCl (r+ / r-) = 0.169 nm/0.181nm > 0.732 cations in cubic hole BCC
• NaCl (r+ / r-) = 0.095 nm/0.181nm 0.732 > (r+ / r-) > 0.414
cations in octahedral holes FCC
• ZnS (r+ / r-) = 0.074 nm/0.184nm 0.414 > (r+ / r-)
cations in tetrahedral holes FCC
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)
Metals and Nonmetals
• MetalsShiny luster, various colors - mostly silver
Malleable and ductile
Good conductors of heat and electricity
Most metal oxides are basic Na2O(s) + H2O(l) ==> 2 NaOH(aq)
Generally form cations
Metals and Nonmetals
• NonmetalsNo luster, various colors
Usually brittle - some hard, some soft
Poor conductors of heat and electricity
Most nonmetallic compounds are acidicCO2(g) + H2O(l) ==> H2CO3(aq)
Generally form anions or oxyanions
Metalloids (Semimetals)
• Intermediate properties between metals and nonmetals
Some metallic characteristics and some nonmetal characteristics
Some, most notably Si, are electrical semiconductors
Periodic Trends in Lattice Energy
Electrostatic Force = (C+) (A-) / Distance
• Ionic Size
• Ionic Charge
Melting and Boiling Points of Some Ionic Compounds
Compound mp( oC) bp( oC)
CsBr 636 1300NaI 661 1304MgCl2 714 1412KBr 734 1435CaCl2 782 >1600NaCl 801 1413LiF 845 1676KF 858 1505MgO 2852 3600
Table 9.1 (p. 340)
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
The Periodic Table of the Elements2.1
0.9 1.5
0.9 1.2
0.8 1.0 1.3
0.8
0.7
0.7
1.0
0.9
1.5 1.6 1.61.5 1.8
1.2
1.1
1.8 1.8 1.9 1.6
1.4 1.6
1.5
1.8
1.7
1.9
1.9
2.2 2.2
2.2
2.2
2.2
1.9
2.4
1.7
1.9
2.0 2.5 3.0 3.54.0
He
Ne
Ar1.5 1.8 2.1 2.5 3.0
1.6 1.8 2.0 2.4 2.8 Kr
Xe
Rn
2.52.1
2.2
1.9
2.01.9
1.81.7
1.81.8
1.1 1.1 1.1 1.1
1.3
1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.21.3
1.5 1.7 1.3 1.3 1.3 1.3 1.3 1.3 1.31.3 1.5
0.9
1.3 2.2
Electronegativity
1.1
Th Pa U Np No Lr
1.3
Ce Pr Nd Pm Yb Lu
Bond Polarity
Nonpolar Covalent Bonds:Electronegativity Difference is ideally 0 Very small differences are still considered to be mostly covalent bonds, up to about 0.4
Polar Covalent Bonds:Electronegativity Difference measurableHas polar covalent characteristics up to 2.0
Mostly Ionic Bonds: High Electronegativity Differences
Bond Polarity
Cl2 is a nonpolar covalent bond E = (3.0 - 3.0) = 0
HCl is a polar covalent bond E = (3.0 - 2.1) = 0.9
NaCl is a very polar bond - ionic E = (3.0 - 0.9) = 2.1
Oxidation-Reduction Reactions
• How can we predict if a oxidation-reduction reaction will occur
• Experimental trials give reactivity relationships
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
Activity Series
Mg ==> Mg2+ has a higher activity than
Zn ==> Zn2+
Therefore:
Mg + Zn2+ ==> Mg2+ + Zn
and
Zn + Mg2+ ==> No Reaction
Activity Series
Cr ==> Cr3+ has a higher activity than
Ni ==> Ni2+
Therefore:
2Cr + 3Ni2+ ==> 2Cr3+ + 3Ni
and
Ni + Cr3+ ==> No Reaction
Basic and Acidic Oxides
• More ionic oxides formed on left side of periodic table
• If dissolve in water form basic solutions
MO(s) + H2O(l) M+2(aq) + 2 OH-(aq)