Transcript CHEMISTRY LAB C

CHEMISTRY LAB C
• Team of 2 students
• 50 minutes
• Safety Requirements
Wear apron or lab coat
OSHA approved goggles with indirect vents
• Do not bring reference material
or calculators
CHEMISTRY LAB C
• A series of stations with various activities
Could Include:
Hands-on Activities: Experiments
Interpretation 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 Conceptually
Predicting and explaining trends
Demonstrated Experimentally
Collecting and/or accounting for data
Topics Covered
Physical Properties
Electronic Structure and Bonding
Chemical Properties
Physical Properties
Atomic and Ionic Radii
Ionization Energy
Melting Point
Electronegativity
Electronic Structure
Electron Configuration
Ionic and Covalent Bonding
Charges on Ions
Metallic Properties
Chemical Properties
Precipitation Formation
(Solubility)
Reaction with Acids
Acidity of Oxides
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
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H
He
Li
Be
B
C
N
O
F
Ne
1s 1
1s 2
1s2 2s 1
1s2 2s 2
1s2 2s 2 2p 1
1s 2 2s 2 2p 2
1s 2 2s 2 2p 3
1s 2 2s 2 2p 4
1s 2 2s 2 2p 5
1s 2 2s 2 2p 6
[He]
[He] 2s 1
[He] 2s 2
[He] 2s 2 2p 1
[He] 2s 2 2p 2
[He] 2s 2 2p 3
[He] 2s 2 2p 4
[He] 2s 2 2p 5
[He] 2s 2 2p6 = [Ne]
Electron Configuration - II
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Na
Mg
Al
Si
P
S
Cl
Ar
[Ne] 3s 1
[Ne] 3s 2
[Ne] 3s 2 3p 1
[Ne] 3s 2 3p 2
[Ne] 3s 2 3p 3
[Ne] 3s 2 3p 4
[Ne] 3s 2 3p 5
[Ne] 3s 2 3p6 == [Ar]
Order of Electron Filling
1s
2s
2p
3s
3p
3d
4s
4p
4d
4f
5s
5p
5d
5f
6s
6p
6d
7s
7p
Electron Configuration - III
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K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
[Ar] 4s 1
[Ar] 4s 2
[Ar] 4s 2 3d 1
[Ar] 4s 2 3d 2
[Ar] 4s 2 3d 3
[Ar] 4s 1 3d 5
[Ar] 4s 2 3d 5
[Ar] 4s 2 3d 6
[Ar] 4s 2 3d 7
[Ar] 4s 2 3d 8
[Ar] 4s 1 3d 10
[Ar] 4s 2 3d 10
Or this order is OK !
[Ar] 3d 1 4s 2
[Ar] 3d 2 4s 2
[Ar] 3d 3 4s 2
Anomalies
to Filling
Either order will be OK !
But it’s normally best to
put the one filling last!!!
Anomalies
to Filling
Orbital Box Diagrams - III
Na
Atomic Number
Element
11 Na
Condensed Electron
Configuration
[He] 3s1
Orbital Box
Diagrams(3s&3p)
3s
12
3px
3py
3pz
[He] 3s23p2
3px
3py
3pz
[He] 3s23p3
P
3px
3py
3pz
[He] 3s23p4
S
Cl
3s
18
3pz
Si
3s
17
3py
[He] 3s23p1
3s
16
3px
Al
3s
15
3pz
[He] 3s2
3s
14
3py
Mg
3s
13
3px
Ar
Ar
3px
3px
3py
3py
3pz
3pz
[He] 3s23p5
[He] 3s23p6
Orbital Box Diagram - IV : Sc
4s
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
Zn
3d
Electronic Configuration Ions
• Na 1s 2 2s 2 2p 6 3s 1
Na+
• 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
N- 3
1s 2 2s 2 2p 6
1s 2 2s 2 2p 3
1s 2 2s 2 2p 6
Fig. 8.23
Atomic Size
Atomic Size
• Across a row
Diameter Decreases
Electrons added to the same shell
More protons pull in electrons closer
• Down a column
Diameter Increases
Electrons fill into further out shells
Fig. 8.13
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 Petit
Product 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
Periodicity of First Ionization
Energy (IE1)
Fig. 8.14
Fig. 8.27
Size of Ions
• Size of anions are larger than atoms
Adding electrons to an atom increases the
size: Higher -/+ ratio
• Size of cations are smaller than atoms
Removing 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)
More Negative
Trends in Three Atomic Properties
Fig 8.18
Fig. 9.2
Metals and Nonmetals
• Metals
Shiny 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
• Nonmetals
No luster, various colors
Usually brittle - some hard, some soft
Poor conductors of heat and electricity
Most nonmetallic compounds are acidic
CO2(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
Lattice Energy
Li+ (g) + F- (g) ==> LiF (s)
DHoLattice of LiF = -1050 kJ
Periodic Trends in Lattice Energy
Electrostatic Force = (C+) (A-) / Distance
• Ionic Size
• Ionic Charge
Melting and Boiling Points of Some
Ionic Compounds
Compound
CsBr
NaI
MgCl2
KBr
CaCl2
NaCl
LiF
KF
MgO
Table 9.1 (p. 340)
mp( oC)
636
661
714
734
782
801
845
858
2852
bp( oC)
1300
1304
1412
1435
>1600
1413
1676
1505
3600
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 Elements
2.1
He
0.9 1.5
2.0 2.5 3.0 3.54.0 Ne
Electronegativity
0.9 1.2
1.5 1.8 2.1 2.5 3.0 Ar
0.8 1.0 1.3 1.5 1.6 1.61.5 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 1.7 1.81.9 2.1 2.5 Xe
0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.2 2.2 2.2 2.4 1.9 1.8 1.8 1.9 2.0 2.2 Rn
0.7 0.9 1.1
Ce Pr Nd Pm
Yb Lu
1.1 1.1 1.1 1.2 1.2 1.1 1.2 1.2 1.2 1.2 1.2 1.2 1.21.3
1.3 1.5 1.7 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.31.3 1.5
Th Pa U Np
No Lr
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 measurable
Has polar covalent characteristics up to 2.0
Mostly Ionic Bonds:
High Electronegativity Differences
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
The Redox Process in Compound Formation
Fig. 4.13
Oxidation-Reduction Reactions
• How can we predict if a oxidation-reduction
reaction will occur
• Experimental trials give reactivity
relationships
Metal Activity
• Higher activity
More the metal wants to be oxidized
More the metal wants to gain electrons
Better 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)
Basic and Acidic Oxides
• More covalent oxides formed on right side
of periodic table
• If dissolve in water form acidic solutions
MO(g) + H2O (l)  H2MO2(aq)
H2MO2(aq) +H2O H3O+(aq) + HMO3(aq)