Today we continued discussing Lewis Structures. I started lecture by covering a couple more examples with the surrounding atom or ligand being a halogen, hydrogen, or an OH- group. We then discussed the differences that occur when oxygen or sulfur is the surrounding atom or ligand. Oxygen containing molecules can readily form double bonds, which leads us to multiple resonance structures that can be drawn. Resonance structures of a given molecule will always have the same energy. In addition to resonance structures structures, since some molecules can expand their octet we discussed choosing structures that have different energies and which one would be the "best" Lewis structure. There are two sets of rules you will be responsible for: The octet rule and formal charges. According to our textbook (pg 324-325) "In general, when choosing between alternate Lewis Structures, if it is possible to draw a Lewis Structure where the octet rule is satisfied without using multiple bonds, that structure is preferred."
We will discuss this more on Friday.
Have fun at Mirror Lake on Thurs night, but be sure to come to class on Friday. Last year I had a student make it to class with their sandals still duct taped to their feet :)
GO BUCKS! BEAT BLUE!
Thursday, November 19, 2009
Tuesday, November 17, 2009
Lecture #22, Monday, November 16th
Today's lecture solely focused on Lewis Structures and I did several examples of various molecules. You will be responsible for the following in terms of Lewis Structures:
*Total # of valence electrons
*Identify the Central Atom
*Identify the Ligands
*Indicate the number of bonding pairs on the central atom
*Indicate the number of lone pairs on the central atom
*Indicate the electron domain geometry of the molecule
*Indicate the molecular geometry of the molecule
*Determine the hybridization of the central atom
*Draw the molecule
*Determine if the molecule is polar or non-polar
On Wed we will continue the talk on Lewis Structures and go through more examples with various different ligands.
The exam was tonight and I will get the average posted as soon as I can.
*Total # of valence electrons
*Identify the Central Atom
*Identify the Ligands
*Indicate the number of bonding pairs on the central atom
*Indicate the number of lone pairs on the central atom
*Indicate the electron domain geometry of the molecule
*Indicate the molecular geometry of the molecule
*Determine the hybridization of the central atom
*Draw the molecule
*Determine if the molecule is polar or non-polar
On Wed we will continue the talk on Lewis Structures and go through more examples with various different ligands.
The exam was tonight and I will get the average posted as soon as I can.
Friday, November 13, 2009
Lecture #21, Friday, November 13th
Today we continued our talk about bonding in molecules by finishing up with non-polar and polar covalent bonds. The larger the difference in electronegativity, the more ionic a bond is and this can enable us to list certain molecules in order of covalent/ionic character.
We then started to talk about Lewis structures and VSEPR shapes. Check out the following link depicting the various VSEPR shapes, which are determined by how many pairs of electrons surround the central atom. We will determine the number of lone pairs and bonding pairs around the central atom based on #1. The number of valence electrons around the central atom and #2. The number of electrons each ligand (or surrounding atom) contributes to each bond.
I will discuss these shapes in great detail on Monday in class and go through various examples. If you are a visual person check out the following website put together by the general chemistry department here at Ohio State. It has an excellent tutorial of what happens to the shapes of molecules as we vary the number of pairs of electrons about the central atom.
I hope everyone has a great weekend :)
We then started to talk about Lewis structures and VSEPR shapes. Check out the following link depicting the various VSEPR shapes, which are determined by how many pairs of electrons surround the central atom. We will determine the number of lone pairs and bonding pairs around the central atom based on #1. The number of valence electrons around the central atom and #2. The number of electrons each ligand (or surrounding atom) contributes to each bond.
I will discuss these shapes in great detail on Monday in class and go through various examples. If you are a visual person check out the following website put together by the general chemistry department here at Ohio State. It has an excellent tutorial of what happens to the shapes of molecules as we vary the number of pairs of electrons about the central atom.
I hope everyone has a great weekend :)
Tuesday, November 10, 2009
Lecture #20, Monday, November 9th
I started lecture with a quick review of Lewis dot notations and talked about ionic and covalent bonding into more detail. I discussed how the forces holding atoms together in these bonds and transitioned into homogeneous diatomic molecules. I put an emphasis on the shared bonding pairs of electrons in these molecules vs. their lone pairs.
Single vs. Double vs. Triple bonds were mentioned and I discussed the relative strength of each of these bonds. We then discussed heterogeneous diatomic molecules and used the periodic trend of electronegativity to determine if a bonding pair of electrons is shared equally. If the bonding pair of electrons is shared equally then we refer to a bond as non-polar. If the electrons are shared unequally the bond is polar.
There is no class on Wednesday :(
On Friday we will start our discussions on drawing Lewis Structures.
Single vs. Double vs. Triple bonds were mentioned and I discussed the relative strength of each of these bonds. We then discussed heterogeneous diatomic molecules and used the periodic trend of electronegativity to determine if a bonding pair of electrons is shared equally. If the bonding pair of electrons is shared equally then we refer to a bond as non-polar. If the electrons are shared unequally the bond is polar.
There is no class on Wednesday :(
On Friday we will start our discussions on drawing Lewis Structures.
Monday, November 9, 2009
Lecture #19, Friday, November 6th
I finished my lecture material for Chapter 7 today by discussing magnetism, or more specifically when an atom is more or less diamagnetic/paramagnetic. If an atom is diamagnetic it does not have any unpaired electrons and if it is paramagnetic it contains unpaired electrons. If one atom has more unpaired electrons than another one, it is more paramagnetic in character.
We then discussed how certain periodic trends, such as ionization energy and radii are interrelated and you should know what effect ionization energy has on the radius of an atom or ion.
Chapter 8 starts with the overall depiction of ionic and covalent bonds. We discussed the main principles of Lewis Theory and how certain principles, such as the octet rule were established. We briefly mentioned how to draw Lewis dot structures and we will use these structures as the background on how to draw Lewis structures and come up with the VSEPR shapes.
You should have all the homework from Chapter 6 and 7 complete and should take the practice exam tonight to see where you are in terms of the rest of the class.
We then discussed how certain periodic trends, such as ionization energy and radii are interrelated and you should know what effect ionization energy has on the radius of an atom or ion.
Chapter 8 starts with the overall depiction of ionic and covalent bonds. We discussed the main principles of Lewis Theory and how certain principles, such as the octet rule were established. We briefly mentioned how to draw Lewis dot structures and we will use these structures as the background on how to draw Lewis structures and come up with the VSEPR shapes.
You should have all the homework from Chapter 6 and 7 complete and should take the practice exam tonight to see where you are in terms of the rest of the class.
Wednesday, November 4, 2009
Exam #2 Monday, November 16th 6:30 pm
The second exam will be held on Monday, November 16th at 6:30 pm. The locations will be posted on carmen as they were for the last exam.
A practice exam will be held Monday, November 9th at 7:00 pm in 1153 Smith Lab. I will hold a review session immediately following the exam.
The exam will cover Chapters 6 and 7.
A practice exam will be held Monday, November 9th at 7:00 pm in 1153 Smith Lab. I will hold a review session immediately following the exam.
The exam will cover Chapters 6 and 7.
Lecture #18, Wednesday, November 4th
I covered some details from Exp #7 and emphasized that in this experiment we are determining which ions are present in a qualitative sense. This means that as a chemist, we do not care how much of a particular substance is present. We just care if it is present or absent. So in measuring out quantities in this lab you do not have to be extremely careful.
I ALMOST finished Chapter 7 today as I discussed ionization energy, electron affinity, and electronegativity. When you are analyzing the ionization energy and electron affinity be sure to WRITE OUT THE ORBITAL BLOCK DIAGRAMS!!! Proper interpretation of these diagrams is the key to properly analyze the trends in ionization energy and electron affinity. Keep in mind that a completely filled orbital is very stable, especially a filled d orbital or the filled s and p combination to form a stable octet. Also, a half filled orbital is fairly stable and accounts for the non-linear trends we observe.
On Friday we will complete Chapter 7 in the first five minutes of class and then go on to chapter 8.
If you are keeping up with the material you should have all the additional homework problems from chapter 6 and chapter 7 complete.
I ALMOST finished Chapter 7 today as I discussed ionization energy, electron affinity, and electronegativity. When you are analyzing the ionization energy and electron affinity be sure to WRITE OUT THE ORBITAL BLOCK DIAGRAMS!!! Proper interpretation of these diagrams is the key to properly analyze the trends in ionization energy and electron affinity. Keep in mind that a completely filled orbital is very stable, especially a filled d orbital or the filled s and p combination to form a stable octet. Also, a half filled orbital is fairly stable and accounts for the non-linear trends we observe.
On Friday we will complete Chapter 7 in the first five minutes of class and then go on to chapter 8.
If you are keeping up with the material you should have all the additional homework problems from chapter 6 and chapter 7 complete.
Monday, November 2, 2009
Lecture #17, Monday, November 2nd
Class tarted today with discussing Chapter 7, which is the Periodic Properties of the Elements. We talked about the tabular arrangement of the elements in the periodic table and the horizontal periods and vertical groups. We separate the elements of the periodic table into two generic groups called the "main group" and "transition metals." We do this due to the different properties of these groups, particularly that the transition metals do not necessarily always have a noble gas electron configuration upon forming ions. We also observe that transition metal ions will lose their s electrons first, then their d electrons when forming an ion.
We then discussed periodic trends starting with metallic character. I then talked about effective nuclear charge, and used that concept to explain the trends in atomic and ionic radii.
On Wed I will talk about ionization energy, electron affinity, electronegativity, and various other periodic trends.
We then discussed periodic trends starting with metallic character. I then talked about effective nuclear charge, and used that concept to explain the trends in atomic and ionic radii.
On Wed I will talk about ionization energy, electron affinity, electronegativity, and various other periodic trends.
Lecture #16, Friday October 30th
After our discussion of electron configurations, we can assign a set of four quantum numbers to each electron in an atom. Chemists are interested in analyzing how electrons interact, so labeling them is important. Be sure to draw out the orbital block diagram to interpret the quantum numbers for each electron.
Each electron has a set of four quantum numbers and we discussed each of them and carried out an example by listing the set of four quantum numbers for the valence electrons in a nitrogen atom.
I ended class by discussing radial and angular nodes and talking about probability density functions. Be sure to read the "A closer look" box on page 230-231 in the textbook.
Each electron has a set of four quantum numbers and we discussed each of them and carried out an example by listing the set of four quantum numbers for the valence electrons in a nitrogen atom.
I ended class by discussing radial and angular nodes and talking about probability density functions. Be sure to read the "A closer look" box on page 230-231 in the textbook.
Lecture #15, Wednesday October 28th
Today we discussed Lab #6, which is the preparation of Alum from Scrap Aluminum. This lab is a prototypical application of calculating theoretical vs. actual yields.
We then discussed how to look at the periodic table to determine the energies of the orbitals and we started to populate these orbitals. Electron counting rules are given as a guide, but we discussed the various exceptions to these rules. We Finished class by discussing the electron configurations of ions and the octet rule. This explains why certain ions want to have the charges they do.
We then discussed how to look at the periodic table to determine the energies of the orbitals and we started to populate these orbitals. Electron counting rules are given as a guide, but we discussed the various exceptions to these rules. We Finished class by discussing the electron configurations of ions and the octet rule. This explains why certain ions want to have the charges they do.
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