Chemical Kinetics #4 -- Reaction pathways, Activation Energy, and Kinetic Reaction Control

Watch the following videos to help understand reaction pathways and activation energy.  The third video helps to explain how catalysts work and the difference between kinetics and thermodynamics.

Chemical Kinetics #3 -- Rate Limiting Step

Watch the following video to help understand what the rate determining step of a reaction is and how it can be used to determine a reaction mechanism.

Chemical Kinetics #2 -- Rate Laws and Rate Constants

Watch the following videos to help understand how to create a rate law for a reaction and how to determine the rate constant from a rate law.

Chemical Kinetics #1 -- Overview and Ways to affect speed of reaction

Watch the following videos to get a good overview of the topics in the Kinetics unit and the specific of how to affect the rate of reactions.

Beer's Law and Spectrophotometry

Watch the first video to help you understand how light can be used as a measurement and analysis tool in chemistry -- pay extra attention to the part about the Beer-Lambert Law.





Watch the second video to get an idea about the next lab we will be doing, Spectrophotometric Determination of Concentration, or Beer's Law.  We will be using a spectrophotometer just like this teacher does in our lab, although ours will be larger and older.

Intermolecular Forces #2: Vapor Pressure, Normal Boiling Point, Triple Point

Watch the following videos to help visualize and understand the concepts of vapor pressure, Pressure-Temperature Phase Diagrams, and the Triple Point -- as all are related to Intermolecular Forces.

Intermolecular Forces #1: IMF's in general and how they work in liquids

Watch the following videos to help you better understand the origins of intermolecular attractive forces, the different types of IMF's and their relative strengths, and how these IMF's create the properties of liquids.

Gases -- Dalton's Law and Graham's Law

Watch these videos to help you gain a better understanding of Pressure and how gases mixed together affect it, as well as how the mass of gas molecules effects their speed of movement.

Gases -- Ideal Gas Law and Real Gases

Watch these videos to help you gain a better understanding of the Ideal Gas Law, how it works in problem solving, and how Real Gases deviate from the Ideal.

Bonding #6 -- Polar vs. Non-Polar Molecules

Watch the following video for a good overview of Molecular Polarity, as well as Inter-Molecular Forces that result between molecules due to their polarities.  (total time = 11 minutes)

Bonding #7 -- Resonance Stuctures and Delocalized Bonding of Electrons in Covalent Molecules

     Read the following text and illustrations to help understand what resonance Lewis Structures actually mean in terms of real molecules.  They involve delocalized bonding, or electrons that are not just shared between two atoms like in a normal ("localized") covalent bond, BUT instead are shared over three or more atoms/across the whole molecule.

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     Look at the following illustration to help understand delocalized pi bonding in molecules that have resonance structures.  Picutre (a) shows a 2-D molecular skeleton.  Picutre (b) shows the skeleton with unhybridized  p orbitals perpendicular to plane of molecule.  Picutre (c) shows  "merged" p orbitals above/below the plane of the molecule, with  delocalized electrons shared over the whole molecular instead of just between two atoms.  And picture (d) showing the electron cloud (made up of the regular covalently bonded electrons in their hybrid orbitals, as well as the delocalized electrons) surrounding whole molecule, with electron density shown by color.

Bonding #5 -- Molecular Shapes and Geometry

Watch the following three videos for a good overview of Molecular Geometry and Shapes, including hybrid orbitals. (total time = 27 minutes)  Also click on the two links for extra information about molecular shapes and hybrid orbitals.


Click on this link to learn about hybrid orbitals.
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/hybrv18.swf








Click on this link for information about actual pictures of real molecules with shapes that match up with VSEPR and hybrid orbital theories!
http://phys.org/news/2013-05-first-ever-high-resolution-images-molecule-reforms.html

Bonding #0 -- Bonding Overview

Watch the following video for a good overview of Chemical Bonding, especially as it relates to Coulumb's Law.  (total time = 10 minutes)

Bonding #4 -- Bond Polarity

Watch the following video for a good overview of Electronegativity and Bond Polarity -- the difference between Ionic Bonds, Polar Covalent Bonds, and Non-Polar Covalent Bonds.  (total time = 9 minutes)

Bonding #3 -- Covalent Bonding, Lewis Structures, VSEPR

Watch the following two videos for a good overview of Covalent Bonding, Lewis Diagrams, and the VSEPR model to explain molecular shapes.

Bonding #2 -- Metallic Bonding

Watch the following two videos for a good overview of Metallic Bonding and the properties of substances held together by metallic bonds, called Metals or Metallic Solids.  (total time = 10 minutes)

Bonding #1 -- Ionic Bonding

Watch the following two videos for a good overview of Ionic Bonding and the properties of substances held together by ionic bonds, called Ionic Solids.  (total time = 10 minutes)

Periodic Table Properties and Trends

Elements have different properties based on the valence electrons in their atoms.  These valence electrons and properties control how the atoms of that element will react with other elements.

Because the number and position of valence electrons an atom has matches up with its location on the Periodic Table, elements with similar valence electrons will have similar properties and are found in the same groups (up and down columns) on the Periodic Table.  In addition, as you go across each row from left to right and down each column on the Table, the elements show patterns in their properties and behaviors based on where they are located in the Table.

Several important properties of atoms we need to know about are:

1. Atomic Size (Radius)
2. Ionic Size (Radius)
3. Ionization Energy
4. Electronegativity

For each of these properties, you need to know what it means, what pattern it shows on the Periodic Table, and why it shows that pattern (what is going on inside the atom with the electrons to make that happen).  These following pictures and link to a flash animation will help with this understanding.

• Atomic Size (Radius) shown as a line graph.

• Atomic Size (Radius) shown as a bar graph in the Periodic Table.

• Click on this link to go to a Flash animation explaining about atomic properties, how they are related to electrons, and the patterns they show in the Periodic Table.

http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/atomic4.swf

• All of the properties and their patterns on the Periodic Table.

Electrons and PES

PES = Photo-Electron Spectroscopy is a special technique used to determine the location and number of electrons in an atom based on their energy.  It is another way of thinking about quantum numbers and it is experimental proof that electron configurations are accurate representations of the location and distribution of electrons within an atom.


Watch the following videos to get an idea of how the technique works and what the graphical results look like.  Then notice how we can use these graphs to get information about the electron configuration and identities of atoms.

• This second video has a worksheet that goes along with it that you will be asked to complete while watching the video.

• Lastly, read the diagram and text below AND the webpage shown in this link to help you understand what is going on with electrons in 3d and 4s, which orbtial they ACTUALLY fill in first, why they do it in that order, and why we learn electron configurations in the other order.

http://www.chemguide.co.uk/atoms/properties/3d4sproblem.html

Electron-electron repulsion

It takes 1312 kJ of energy to remove the electron from a mole of hydrogen atoms.  What might we expect this value to be for helium?  Helium contains two electrons, but its nucleus contains two protons; each electron "sees" both protons, so we might expect that the electrons of helium would be bound twice as strongly as the electron of hydrogen. The ionization energy of helium should therefore be twice 1312 kJ/mol, or 2612 kJ/mol. 

However, if one looks at the spectrum of helium, the continuum is seen to begin at a wavelength corresponding to an ionization energy of 2372 kJ/mol, or about 90% of the predicted value.

Why are the electrons in helium bound less tightly than the +2 nuclear charge would lead us to expect? 

The answer is that there is another effect to consider: the repulsion between the two electrons; the resulting electron-electron repulsion subtracts from the force holding the electron to the nucleus, reducing the local binding of each.

Electron-electron repulsion is a major factor in both the spectra and chemical behavior of the elements heavier than hydrogen. 

Unpaired Electrons: Paramagnetism and Diamagnetism

     Watch the two videos that follow to help you understand the difference between paramagnetism and diamagnetism, as well as how each phenomenon is caused by unpaired and paired electrons in atomic orbitals.  Also, check out the liquid oxygen in the second video!   (Total time = 10 minutes)