chemistry 201 –final exam -...
TRANSCRIPT
Chemistry 201 – Final Exam 1
(C) Pavel SedachLearnfaster.ca
Questions? Suggestions? E-mail me and I will try to find time to reply. [email protected]
All the best!
� Lecture Slides� Booklet Solutions� Test Solutions� Extra notes and advice� Advice on which exams and questions to write� Corrections
Available December 8th at:http://learnfaster.ca/blog/chem-201-final/
Thursday, December 8, 2016
5:00 pm to 6:30 Molecular Orbital Theory
6:30 to 7:00 Break
7:00 to 8:15 Functional Groups through VSEPR
8:15 to 8:30 Break
8:30 to 10:00 pm Hybridization and VSEPR
Friday, December 9, 2016
5:00 pm to 6:30 Intermolecular Forces in Detail
6:30 to 7:00 Break
7:00 to 8:15 Isomers and Review
8:15 to 8:30 Break
8:30 to 10:00 pm Review
����
MO Theory – �� 4
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*we assume here that our bond forms along the x-axis
���� ����� ��������� � ����������� ����������
�
B.O.=
Ener
gy
2s
F F
2p
2s
2p
����
���
�����
����
����
����� ����
�
��� ��� ��� ��� ��� ���
MO Theory – �� 5
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*we assume here that our bond forms along the x-axis
���� ����� ��������� � ����������� ����������
��
ABMO
Anti-Bonding Molecular Orbital
Ener
gy
2s
F F
2s
����
��� BMOBonding Molecular Orbital
NBMONon-Bonding Molecular Orbital
2s 2s
2s 2s
MOs of �� 6
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σ-bonding interaction
π-bonding interactionEner
gy
F F
2p
��������
�����
����
����� ����
�
2p
MO Theory – �� 9
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VSEPR Predicts
O O
MO Theory Predicts
O O
Ener
gy
2s
2p
2s
2p
OO
MO Theory –�� 10
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2s
2p
2s
2p
ON
VSEPR Predicts
N O
MO Theory Predicts
N O
Ener
gy
MO Theory – ��� 11
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2s
2p
2s
2p
OF
VSEPR Predicts
F O
MO Theory Predicts
F O
Ener
gy
MO Exceptions – Homonuclear Diatomics�� and smaller 12
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VSEPR Predicts
MO Theory Predicts
All exceptions:
��� ���� ���� ���� ��� ��� ��
Literally every homonucelardiatomic smaller and including ��.
2s
2p
2s
2p
NN
N N
Ener
gy
MO Theory – Does �� exist? 13
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VSEPR Predicts
MO Theory Predicts
All exceptions:
��� ���� ���� ���� ��� ��� ��
Literally every homonucelardiatomic smaller and including ��.
2s
2p
2s
2p
BB
B B
Ener
gy
Intramolecular Bonding 15
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The type of bond a compound forms is based on electronegativityElectronegativity is a measure of how much an atom attracts electrons in the bond in molecule
Ionic BondingCovalent Bonding0 1.7 3.4
��� ����
homonucleardiatomics
electron sharing electron transfer
� ��
dipole moment
� � � �
�� � ��� �� � ���
��� � ��� � ��� � ��� Covalent
0.5
VSEPRSummary
16
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��� / ��
E Shape: linearM Shape: linear
��� / ���
���� / ���
E Shape: trigonal planarM Shape: trigonal planar
E Shape: trigonal planarM Shape: bent, < 120°
��� / ���
���� / ���
E Shape: tetrahedral or TdM Shape: tetrahedral or Td
E Shape: tetrahedral or TdM Shape: trigonal pyramidal
����� / ���
E Shape: tetrahedral or TdM Shape: bent, < 109.5°
��� / ����
E: trigonal bipyramidalM: trigonal bipyramidal
���� / ����
E: trigonal bipyramidalM: see-saw
����� / ����
E: trigonal bipyramidalM: T-shaped
��� / �����
E: Octahedral (Oh)M: Octahedral (Oh)
���� / �����
E: Octahedral (Oh)M: Square Pyramidal
����� / �����
E: Octahedral (Oh)M: Square Planar
����� / ����
E: trigonal bipyramidalM: linear
�����
����
���
���
��
Systematic Lewis Structures 17
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Step 1 – Count the total number of valence electrons in the structureStep 2 – Arrange the peripheral atoms around the central atom/structure and single bond themStep 3 – Place remaining electrons around peripheral atoms. Place any extra electrons around the central atom.Step 4 – Calculate the formal charges and minimize it by preparing resonance structures
Formal Charge = Valence electrons – lone pair electrons – bonds
Incomplete Valence: ��� Expanded Valence: ����
Systematic Lewis Structures 18
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Step 1 – Count the total number of valence electrons in the structureStep 2 – Arrange the peripheral atoms around the central atom/structure and single bond themStep 3 – Place remaining electrons around peripheral atoms. Place any extra electrons around the central atom.Step 4 – Calculate the formal charges and minimize it by preparing resonance structures
Formal Charge = Valence electrons – lone pair electrons – bonds
Expanded Valence: ��� ����
Understanding Line Diagrams 19
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C has 4 bonds, N has 3 bonds, O has 2 bonds.
To save time drawingstructures, we form line diagrams
Because C behaves so reproducibly and forms 4 bonds, we can use line diagrams to represent organic structures. Every vertex(intersection of 2 or more lines) is a carbon atom and it is assumed that C forms 4 bonds
Understanding Line Diagrams 20
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Draw a condensed diagram (e.g. where there is a carbon and hydrogen, write CH)
Functional Groups 21Priority Group
1Carboxylic Acids
2Esters
3Amides
4Aldehydes
5Ketones
6 Alcohols
7Amines
8 Ethers
9Alkenes
10 Alkynes
11 Alkyl Halides
12 Alkanes ���
Understand naming, structure and bonding for all groups listed
What functional groups are found in the following compound?
Are there any lone pairs missing?
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Drawing Proper Tetrahedral Shapes 22
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There are VERY few ways to draw a proper tetrahedral structure. Fundamental structures are circled above in the same color.
For organic structures, we typically put a straight chain and just have wedge/hash poking out to one side:
All of these drawings represent EXACTLY the same molecule viewed from different angles
What is wrong with the structures below?
Functional Groups 23(C) Pavel Sedach Learnfaster.ca
Name the functional group. Draw any missing lone pairs. Name the compound.Give the shape around each atom AND state whether it is drawn correctly according to VSEPR:
correct? correct? correct? correct?
Functional Groups 24(C) Pavel Sedach Learnfaster.ca
Name the functional group. Draw any missing lone pairs. Name the compound.Give the shape around each atom AND state whether it is drawn correctly according to VSEPR:
correct? correct? correct? correct?
Functional Groups 25(C) Pavel Sedach Learnfaster.ca
Name the functional group. Draw any missing lone pairs. Name the compound.Give the shape around each atom AND state whether it is drawn correctly according to VSEPR:
correct? correct? correct?
Resonance, Bond Order and Average Charge 26
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Identify the major, minor and intermediate resonance contributors:
����
Does the above compound have an effective resonance hybrid?
Resonance, Bond Order and Average Charge 27
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Identify the major, minor and intermediate resonance contributors:
���
Does the above compound have an effective resonance hybrid?
Single, Double and Triple Bonds 32
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Bond Strength and Bond Dissociation Energy (Bond Energy)
Bond Length
Single Bond Double Bond Triple Bond
< <
> >Single Bond Double Bond Triple Bond
Orbital Hybridization (Valence Bond Theory) 33
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Count the number of things attached, count the number of orbitals used!
s
p
d
s
p
s
p
s
p
+
What is the energy diagram for the hybridized atom? 34
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Energy diagram ofUnhybridized C
Unhybridized N
Unhybridized O
2s
2p
2s
2p
2s
2p
� and � Bonding Frameworks – aka. Valence Bond Theory 35
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Valence bond theory is an extension of VSEPR. The two are distinct from MO theory.
� Bonding Framework � Bonding Framework
X
X
X
X
x-axis
� and � Bonding Frameworks – aka. Valence Bond Theory 36
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� Bonding Framework � Bonding Framework
X X
� and � Bonding Frameworks – aka. Valence Bond Theory 37
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� Bonding Framework � Bonding Framework
y y
VSEPR Structure Hybridization Electronic Shape Molecular Shape Bond Angles Notes
��� �� linear linear 180�
��� ��� trigonal planar trigonal planar 120�
���� ��� trigonal planar bent, < 120� < 120� Always has a net dipole
��� ��� tetrahedral or Td tetrahedral or Td 109.5�
���� ��� tetrahedral or Td trigonal pyramidal < 109.5� Always has a net dipole
����� ��� tetrahedral or Td bent, < 109.5� < 109.5� Always has a net dipole
��� ���� trigonal bipyramidal
trigonal bipyramidal 120�, 90� *180� is also a possible angle if looking axial to axial
���� ���� trigonal bipyramidal
see-saw 120�, 90�, 180� Always has a net dipole. 180� is axial to axial. Equator has more room so lone pairs go there (120� > 90� so more room at equator)
����� ���� trigonal bipyramidal
t-shaped 90�, 180� Always has a net dipole. 180� is axial to axial
����� ���� trigonal bipyramidal
linear 180� 180� is axial to axial
��� ����� octahedral or Oh octahedral or Oh orsquare bipyramidal
90�
���� ����� octahedral or Oh square pyramidal 90�, < 90� Always has a net dipole
����� ����� octahedral or Oh square planar 90�
����� � unlikely ����� octahedral or Oh t-shaped < 90� Always has a net dipole. Never experimentally observed.
����� � unlikely ����� octahedral or Oh bent, < 90� < 90� Always has a net dipole. Never experimentally observed.
38© Pavel Sedach Learnfaster.ca
Does the molecule have resonance? 39
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Resonance is movement of electrons through � bonds
ISOMERS42
Look for a carbon atom with 4 different groups
Not Isomers
IsomersDo the compounds have the same molecular formula?
ConstitutionalStereoisomers
Can the compounds be interconverted by rotation about single bonds?
Conformational Configurational
Is the isomerism at a double bond?
Geometric
YESNO
YES NO
Are the atoms connected the same way?
YES NO
YES NO
Optical
Constitutional
Conformational
Geometric
Optical
Same formula (�����), different skeleton!
E-but-2-en-1-olZ-but-2-en-1-ol
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Rotate around single bond
Isomers
trans-but-2-en-1-ol
Not Isomers
Isomers
Do the compounds have the same
molecular formula?
Constitutional
StereoisomersCan the compounds be interconverted
by rotation about single bonds?
Conformational
Configurational
Is the isomerism at a double bond?
GeometricOptical
YES
NO
YES
NO
Are the atoms connected the
same way?
YES
NO
YESNO
e.g. �����vs. ����
����� �����
cis-but-2-en-1-olLook for a carbon atom with4 different groups attached
Newman Projections and Conformational Isomers (conformers) of Ethane
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45
Eclipsed
�
� �
Ener
gy
�
� �
�
� �Staggered
Eclipsed
Staggered
�
�
�
�
� �
�
�
�
Isomers
trans-but-2-en-1-ol
Not Isomers
Isomers
Do the compounds have the same
molecular formula?
Constitutional
StereoisomersCan the compounds be interconverted
by rotation about single bonds?
Conformational
Configurational
Is the isomerism at a double bond?
GeometricOptical
YES
NO
YES
NO
Are the atoms connected the
same way?
YES
NO
YESNO
e.g. �����vs. ����
����� �����
cis-but-2-en-1-olLook for a carbon atom with4 different groups attached
Configurational Isomers - Optical Isomers 47
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4 different groups bonded to one atom (usually Carbon)
Is the following molecule chiral? (optically active)? If so, draw its optical isomer.
Configurational Isomers – Geometric Isomers 48
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cis/trans
longest carbon chain
E/Zlargest atom (Cahn Ingold Prelog Rules)
Which molecule is the most stable? Why? 49
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Does the following compound have a geometric isomer?
Does the following compound have a conformational isomer? A geometric isomer?
Basic Intermolecular Forces 51
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London Dispersion Forces (Van Der Waals Forces) Dipole-Dipole Bonding
��� - GAS
��� - LIQUID
�� - SOLID
Compound – State at 25° C
Basic Intermolecular Forces 52
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Hydrogen Bonding – occurs in the FON elements (HF, OH, NH)
The relative strength of London Dispersion (temporary dipole) forces to Dipole Forces to Hydrogen Bonding isLDF : DD : HB of 1:10:1000
Effects of Intermolecular Forces on Boiling Point 53
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Arrange the following from high to low boiling point
Review 54
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Methyl ethyl ether is a gas at room temperature (boiling point = 8°C), but 1-propanol is a liquid (boiling point = 97°C). This
difference can be explained mostly by:
a) Covalent bonding
b) London Dispersion forces
c) Dipole-dipole interactions
d) Hydrogen bonding
Review 55
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Which of the following has the highest boiling point at 1 atm?
�� ���
�� ���
�� ����
�� ���
Review 56
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Rank the following compounds on the basis of decreasing boiling point:
�� ���� � ������
��� ������������
���� �������������
��� ��������������
�� �� � � � ��� � ��
�� �� � ��� � � � ��
�� � � �� � ��� � ��
�� � � ��� � �� � ��
The ability to stack and London dispersion forces: 57
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There is a relationship between some of the compounds below. What is the relationship and which compounds share it?
Arrange all of the above compounds in order of boiling point (high to low)
Expanded Intermolecular Forces for Mixed Solutions 58
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Interaction Factors of Interaction
(London dispersion forces)Induced dipole-induced dipole
Polarizability
Dipole-induced dipole
Dipole moment of polar molecule and polarizability of nonpolar molecule.
Dipole—dipole
Dipole moment
Ion-induced dipole
Ion and a compound that has LDF only
Ion-dipole
Ion charge, magnitude of dipole
Hydrogen bonding
Molecule contains H-F or O-H or N-HCan hydrogen bond to secondary molecule that has F, O or N with a free lone pair and no Hs
What type of IMFs do the two compounds exhibit towards one another? 59
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What type of IMFs do the two compounds exhibit towards one another? 60
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What type of IMFs do the two compounds exhibit towards one another? 61
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���
���
���
���
Can apply to materials – e.g. hydrophilic vs. hydrophobic 62
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hydrophilic
Reactions 63
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Show the reaction of lithium hydroxide with ethanoic acid
Show the reaction of ammonia with boron trifluoride
Reactions 64
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Show the reaction of triethylamine with butanoic acid
Show the reaction of sodium oxide with water
Electronic Configurations and Quantum Numbers 66
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p
n
+
e-n=1
n=2
n=3
n=4n=5
n=∞
Zinc
Cadmium
Arsenic
Copper
*What are all the exceptions to electron filling?
Vanadium (V): ���������������������
OR [Ar] ������
Ge:
Ti:
As �������������������������
Zn:
Ag:
The Valence Electrons are the highest n-value and highest energy orbitals, including the d-orbitals ONLY if they are unfilled!
Put a square around core electrons and circle the valence electrons 67(C) Pavel Sedach Learnfaster.ca
s orbitals
p orbitals
d orbitals
Electronic Configurations 68
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Which element is depicted in the diagram below?
Energy
n = 1
n = 2
n = 3
n = 4
n = 5
1s
2s
3s
4s
5s
2p
3d
3p
n = �
Aufbau Principle (Low to High Energy)Hund’s Rule (Single before Pairing)Pauli Exclusion Principle
Diamagnetic? Paramagnetic?
Draw the Electronic Configuration for Co 69
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Is cobalt paramagnetic or diamagnetic?
Energy
n = 1
n = 2
n = 3
n = 4
n = 5
1s
2s
3s
4s
5s
2p
3d
3p
Quantum Numbers 70
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Symbol Possible values
Principal Quantum Number ��� (Shell/Energy Level) � ������ � ��
Angular Momentum QN (�) (Subshell or Orbital Shape) � ��� �� �� �� �� �� ������ � � � � �
Magnetic QN (��) (Specific Orbital in Subshell) �� ��� � � �� � ���
Electron spin (��) (Orientation of e- whether up or down) �� �����
� � �� � �� � �
�� �� ��
�� � �� � �
SHAPE
SIZE
ORIENTATION
Electronic Configurations 71
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What are the quantum numbers of the circled electrons?
Energy
n = 1
n = 2
n = 3
n = 4
n = 5
1s
2s
3s
4s
5s
2p
3d
3p
n = �
What atom can this possibly be?
Periodic Properties 72
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������������������ ���������������������������������������
Atomic Radius
����������
Ato
mic R
adiu
s
Effective Nuclear Charge ���� � � � � 73
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Effective nuclear charge = # protons - # core electrons.
It’s essentially an estimate of the number of protons pulling that electron in towards the atom.If an electron feels a higher effective nuclear charge, it is HARDER to remove.
���� Increases left to right across the periodic table. Due to the way ���� is calculated in Chem 201, we don’t see a decrease going down a Group but we should. ���� for the d-block is generally not discussed but even unfilled d acts as core ��.
B C N O
Protons 5 6 7 8
Core Electrons 2 2 2 2
���� 3 4 5 6
����
Ionization Energy is the energy needed to remove an e- from an atom (endothermic) 74
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Explain why the ionization energy of Mg is greater than Al?
F is greater than O?
Ne is greater than F?
Why does period 3 have a greater ionization energy than period 4?
+475
+675
+875
+1075
+1275
+1475
+1675
+1875
+2075
1 2 3 4 5 6 7 8
1st
Ion
izat
ion
En
ergy
(kJ
/mo
l)
Column/Group (not including the d-block)
Period 2
Period 3
Ionization energy (kJ/mol) is ALWAYS endothermic (it always takes energy to remove electrons from an atom!)
Equation for Ionization: � � �� � ��
Successive Ionization Energies of Carbon 75
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The second ionization energy for an atom is always greater than the first. Why?
Where is there an enormous jump in ionization energy and why?
Ionization energy Enthalpy��
���Beginning Shorthand
ConfigurationEquation Final Shorthand
Configuration
1st 1087[He]
� � �� � ��[He]
2nd 2353[He]
�� � ��� � ��[He]
3rd 4621[He]
��� � ��� � ��[He]
4th 6223 ��� � ��� � ��
5th 37831 ��� � ��� � ��
Electron Affinity - Magnitude of how exothermic the absorption of an electron is. 76
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Why does Nitrogen have a lower electron affinity than Oxygen?
What process is described by the enthalpy of attachment of the second electron of Aluminum?
Electron Affinity (kJ/mol)
Review 77
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What is the ���� of the Group 1 elements and the Group 2 elements?
Why is the ionization energy of the Group 15 elements higher than that of the Group 16 elements?
Why is the ionization energy of N bigger than Sulfur?
N, +1402
P, +1012As, +947
O, +1314
S, +1000
Se, +941+925
+1050
+1175
+1300
+1425
2 3 4
1st
Ion
izat
ion
En
ergy
(kJ
/mo
l)
Period/Row (n=2,3,4)
Group 15
Group 16
Large Radii
Atomic Radius is the distance from the nucleus to the outermost electrons. 78
Atomic radius decreases from left to right and across the periodic table.Atomic Radius increases from top to bottom of the periodic table.
Increasin
g Size
Increasing Size
Small Radii
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Ionic Radius
Cations are ALWAYS smaller than their neutral atomsAnions are ALWAYS larger than their neutral atoms
Loses Electron
Gains Electron
Anion
�����
Cation Neutral
Review 79
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1. What are the four periodic trends and how do they vary on the periodic table?
2. What are the exceptions to some trends and why do they occur?
3. Rank the following in order of ionic radius:
���� ���� ��� ���� ���
Orbital Diagrams of the 2s 80
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+r
��
�
��
-r
BOUNDARY DIAGRAMs(also known as LOBE DIAGRAMs)
RADIAL PROBABILITY DIAGRAM
ELECTRON DENSITY DIAGRAM(also known as SCATTER or DOT DIAGRAMs)
r
��
RADIAL PROBABILITY DIAGRAM(typical view)
“spherical” or “radial” node
subshell 1s 2s 3s 2p 3p 3d
� 1 2 3 2 3 3
� 0 0 0 1 1 2
spherical nodes
0 1 2 0 1 0
Radial Probability
Diagram
Scatter Dot Diagram
The following shows the shapes of the radial distribution functions of the atomic orbitals 81
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VSEPR – Subsets of Trigonal Bipyramidal (��� Type) Structures – Self Study 82
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Axial positions are at an angle of 90° to the triangle in the middle of the structure. The equatorial positions form thetriangle in the middle and are at an angle of 120° to each other.
��� ����
Example: ���� Example: ���Electronic Shape: trigonal bipyramidalMolecular Shape: trigonal bipyramidal
Electronic Shape: trigonal bipyramidalMolecular Shape: see-saw
VSEPR – Subsets of Trigonal Bipyramidal (��� Type) Structures 83
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����� �����
Example: ���� Example: ����
Electronic Shape: trigonal bipyramidalMolecular Shape: T-shaped
Electronic Shape: trigonal bipyramidalMolecular Shape: linear
VSEPR – Subsets of Octahedral (�� or ��� Type) Structures 84
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When all atoms are equivalent, the AX6 shape is a perfect octahedron (eight sided shape). This gives rise to all positions being equivalent and all angles being 90° all around.
Electronic Shape: Octahedral (Oh)Molecular Shape: Octahedral (Oh)
��� ���������
Electronic Shape: Octahedral (Oh)Molecular Shape: Square Pyramidal
Electronic Shape: Octahedral (Oh)Molecular Shape: Square PlanarExample:
���
Example: ����
�
Example: ����