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Shapes of Molecules & Ions

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Bianca Mesqueue

on 13 November 2013

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Transcript of Shapes of Molecules & Ions

Shapes of Molecules & Ions
Problem
With the given instructions, can the students accurately build a molecular model of specified atoms and later understand its geometrical shape and predict the molecule's properties and polarity?
Prediction
Given the fact that each type of bond has its own properties, and so do the elements that are bonding, the students will be able to predict their model as well as polarity due to their specific properties.
Terms:
Molecules Assigned
The investigators were assigned different types of molecules for the purpose of identification in the following areas:
Molecular Geometry
Nomenclature
Bond Angles
Type of Bond (covalent polar or non polar)
Lewis Structure
Hybridization of the Central Atom
Presence or Absence of Pi Bonds
VSEPR
# of Ve
"Unknown Molecule"
Molecule #1
Nomenclature:
Nitrate Ion
# of Ve:
24
Type of Bond:
Covalent Polar
Hybridization of the Central Atom:
sp2
Pi Bonds:
Presence

Resonance:
Yes
VSEPR:
The three atoms surrounding the central atom have a VSEPR of 120. they repulse each other .
Molecule #3
Geometrical Structure
Lewis Structure
Molecule #2
Geometric Structure
Nomenclature:
Antimony Pentafluoride
# of Ve:
40
Type of Bond:
Covalent Polar
Hybridization of the Central Atom:
sp3
Absence of Pi Bonds
Resonance:
None
VSEPR:
The five atoms surrounding the central atom have a VSEPR that separates the 5 angles equitable in to 72 angles.
Post-Lab Questions
Question #4:
What geometries tend to be present in polar molecules?
Geometrical Structure
Lewis Structure
Molecule #4
Geometric Structure
Nomenclature:
Carbonyl Fluoride
# of Ve:
24
Type of Bond:
Covalent Polar
Hybridization of the Central Atom:
sp2
Presence of Pi Bonds
Resonance:
None
VSEPR:
The three elements surrounding the hybridization of the Central have an VSEPR that maintains the atoms at a 120 degree angle.
Unknown Molecule
Nomenclature:
Formaldehyde
# of Ve:
12
Type of Bond:
Covalent Polar
Hybridization of the Central Atom:
sp2
Pi Bonds:
Presence
Resonance:
None
VSEPR:
The three atoms surrounding the principal atom contain a VSEPRA of 120. basically on their own.
Geometric Structure
Explain how a molecular shape is predicted. What is the determining factor?
Question #8:
Trigonal Planar
Tetrahedral
Square Pyramidal
Trigonal Pyramidal
Trigonal Planar
Nomenclature:
Tetrachloroidate
# of Ve:
36
Type of Bond:
Covalent Non-polar
Hybridization of the Central Atom:

sp2
Presence or Absence of Pi Bonds:
None
Resonance:
No resonance
VSEPR:
The four atoms surrounding the hybridization atom are separated equally from each other at a 90 degrees angle.
Resonance in Molecule #1
Lewis Structure
Lewis Structure
Lewis structure
A molecular shape can be predicted utilizing the following elements: polarity, VSEPR, hybridization, and the number of valence electrons. Those characteristics give you quite defined model of what could be your molecule. Out of all the characteristics presented before, the most important one to determine a molecular shape is the Valence Shell Electron Pair Repulsion. This method, discovered by Gillespie and Nyholm, states that the localization of the orbitals will ALWAYS maintain a certain distance due to the fact that they repulse themselves because of their magnetism.

Conclusion
Reflection
Triagonal planar, tethrahedral, pyramidal...
All geometrical shapes mentioned above have the common factor that they have the potential of being asymmetric, or have radial asymmetry (vertical and horizontal), depending on the elements that compose the molecule and the valence electrons of each element. This means that when divided by the half, the shape WON'T be the same in both sides. We can arrive to the conclusion because, given the previous explanation, polar bonds tend to compile various shapes.
Resonance
- is a way of describing
delocalized electrons within certain
molecules or polyatomic ions where the bonding cannot be expressed by one single Lewis formula.

Valence Shell Electron-Pair Repulsion theory (VSEPR)
- this theory assumes that each atom in a molecule will achieve a geometry that minimizes the repulsion between electrons in the valence shell of an atom.

Hybridization
- is the concept of mixing atomic orbitals into new hybrid orbitals, suitable for the pairing of electrons to form chemical bonds in the valence bond theory. Hybrid orbitals are very useful in the explanation of molecular geometry nd atomic bonding properties.
Formal Charges
- are apparent charges on certain atoms in a Lewis structure that arise when atoms have not contributed equal numbers of electrons to the covalent bonds joining them.
Throughout the process of this laboratory the investigators could prove that with the use of certain strategies, such as: VSERP, resonance, Hybridization, and the molecule's nomenclature, it is simpler to determine what molecule is being observed. As it has been proven, the investigators could determine the molecules' geometric structure utilizing certain characteristics. Therefore, with the application of these specific characteristics the investigators could observe how electrons of different elements react in the presence of each other.
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