Lab Report 6
Maulik Masaliya
Experiment 6: VSEPR and molecular shape “How does it look?”
October 8, 2020.
Summary:
In this experiment we will be using the WebCSD database to study shapes of molecules by
analyzing experimental crystal structure data. We will also be using our knowledge about
VSEPR theory from the previous experiment to determine the preferred shapes of molecules.
Introduction:
The purpose of this experiment to use the VSEPR theory to study and visualize some more
complex molecules using the WebCSD database. The VSEPR theory allows for determining the
shape of a molecule based on the number of electron pairs that surround the central atom of the
atom and the arrangement. We will predict molecular shapes using the number of electron
bonding pairs, lone pairs and bond order which we learned in the previous experiment.
Materials:
Lab Manual
Laptop (WebCSD database)
Focus questions:
1. What is VSEPR theory, and how can it be used to predict molecular shapes?
VESPR theory is a model that use to predict molecular shape using the steric
number, number of electron bonding pairs, lone pairs, etc. According to this
theory, molecules will rearrange themselves in a way where there is minimum
repulsion between electron pairs/ lone pairs.
2.
Can the structure of simple molecular substances be illustrated by drawing or
building? Why and why not?
Yes, we can draw the Lewis structures which helps us visualize the bonding
(number of lone pairs, bond order). It also helps us see the polarity and
electronegativity of the compounds.
What about more complex molecules? Explain.
Yes, we can use the same concept of Lewis structures to study more complex
molecules. However, it will be more difficult or complicated. Constructing 3D
diagrams would make it easier.
3. How are models and theories useful in helping to explain the structure and behavior of
matter?
Many great scientists have provided us with theories and models which helped
humankind understand chemistry. Over the past few centuries, these theories
discovered the structure of atoms, components within the atom. Theories in the
thermodynamics field created the basis of understanding chemical equations. For
example, Dalton theory further specified the following concepts:
, Matter is composed of very small particles called atoms.
All atoms of a given element are identical.
Atoms cannot be created, destroyed, or subdivided.
In chemical reactions, atoms combine with or separate from other atoms.
In chemical reactions, atoms combine with each other in simple, whole-number
ratios to form combined atoms.
Experiment/ Observation:
Part 1
Molecule name shape Bond angle Predicted bond angle
PF6- Octahedral 90.1, 89.4, 90°
90.4, 179.6
BrF6- Octahedral 90,89.4, 89.7, 90°
178.2
I 3- Linear 180 180°
In(CH3)3 Trigonal pyramidal 124.1, 116.2, 120°
119.6
BeF42- Tetrahedral 109.5 109.5°
NH4+ Tetrahedral 114.9, 109.5, 109.5°
108
SbF6- Octahedral 179.5, 88.7, 90°
91, 89.4
Part 2
Molecule name shape
XeF5 Square pyramidal (octahedral)
H 2O Bent (tetrahedral)
[ClF4-] Square planar (octahedral)
[SbBr5 2-] Square pyramidal (octahedral)
Part 3
Maulik Masaliya
Experiment 6: VSEPR and molecular shape “How does it look?”
October 8, 2020.
Summary:
In this experiment we will be using the WebCSD database to study shapes of molecules by
analyzing experimental crystal structure data. We will also be using our knowledge about
VSEPR theory from the previous experiment to determine the preferred shapes of molecules.
Introduction:
The purpose of this experiment to use the VSEPR theory to study and visualize some more
complex molecules using the WebCSD database. The VSEPR theory allows for determining the
shape of a molecule based on the number of electron pairs that surround the central atom of the
atom and the arrangement. We will predict molecular shapes using the number of electron
bonding pairs, lone pairs and bond order which we learned in the previous experiment.
Materials:
Lab Manual
Laptop (WebCSD database)
Focus questions:
1. What is VSEPR theory, and how can it be used to predict molecular shapes?
VESPR theory is a model that use to predict molecular shape using the steric
number, number of electron bonding pairs, lone pairs, etc. According to this
theory, molecules will rearrange themselves in a way where there is minimum
repulsion between electron pairs/ lone pairs.
2.
Can the structure of simple molecular substances be illustrated by drawing or
building? Why and why not?
Yes, we can draw the Lewis structures which helps us visualize the bonding
(number of lone pairs, bond order). It also helps us see the polarity and
electronegativity of the compounds.
What about more complex molecules? Explain.
Yes, we can use the same concept of Lewis structures to study more complex
molecules. However, it will be more difficult or complicated. Constructing 3D
diagrams would make it easier.
3. How are models and theories useful in helping to explain the structure and behavior of
matter?
Many great scientists have provided us with theories and models which helped
humankind understand chemistry. Over the past few centuries, these theories
discovered the structure of atoms, components within the atom. Theories in the
thermodynamics field created the basis of understanding chemical equations. For
example, Dalton theory further specified the following concepts:
, Matter is composed of very small particles called atoms.
All atoms of a given element are identical.
Atoms cannot be created, destroyed, or subdivided.
In chemical reactions, atoms combine with or separate from other atoms.
In chemical reactions, atoms combine with each other in simple, whole-number
ratios to form combined atoms.
Experiment/ Observation:
Part 1
Molecule name shape Bond angle Predicted bond angle
PF6- Octahedral 90.1, 89.4, 90°
90.4, 179.6
BrF6- Octahedral 90,89.4, 89.7, 90°
178.2
I 3- Linear 180 180°
In(CH3)3 Trigonal pyramidal 124.1, 116.2, 120°
119.6
BeF42- Tetrahedral 109.5 109.5°
NH4+ Tetrahedral 114.9, 109.5, 109.5°
108
SbF6- Octahedral 179.5, 88.7, 90°
91, 89.4
Part 2
Molecule name shape
XeF5 Square pyramidal (octahedral)
H 2O Bent (tetrahedral)
[ClF4-] Square planar (octahedral)
[SbBr5 2-] Square pyramidal (octahedral)
Part 3
