Chemistry Notes for the week of 4/25 - 4/29
Chemistry Notes for the week of 4/25 - 4/29 CHEM - 10060 - 001
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This 5 page Class Notes was uploaded by Nick Manning on Sunday May 1, 2016. The Class Notes belongs to CHEM - 10060 - 001 at Kent State University taught by TBA in Fall 2015. Since its upload, it has received 13 views. For similar materials see GENERAL CHEMISTRY I in Chemistry at Kent State University.
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Date Created: 05/01/16
CHEM I NOTES 9 More important information to cover about Covalent bonds is coming at’cha. We know Covalent Bonds - Share e- (have specific bond angle & bond lengths) - Create molecular substances (unique/distinct units) - Covalent bonds differ widely in the properties, only similar thing is that they are all NONCONDUCTORS There’s also a different type of covalent bonNetwork Covalent Substances - Network Solids: o Systems of covalent bonds that once broken cannot be repaired o They are very hard and strong, with very high Melting Points (MP) and high Boiling Points (BP) Diamonds are a great example of this. Molecular Covalent Substances - Molecular Units remain intact during a phase change, making them reversible o Due to intermolecular forces “nonbonding interactions” “Bonding interactions” include: covalent, ionic, and metallic bonds Intermolecular Forces 1.)London Dispersion Forces - Exists b/wALL particles - It is the reordering of electron rich and electron poor areas when excited by another atom. o When another atom approaches, the original shows its “best side” (the side with either more or less electrons o Original atom becomes temporarily polarized - Weak attractions form - NON-DIRECTIONAL : stronger bonds with greater contact, so the attraction becomes stronger for larger particles with greater surface area - Chief interaction foNONPOLAR molecules 2.) Dipole-Dipole Attractions - Occur b/w all Polar Molecules - Permanent Polarization - Opposite poles of dipoles attract - STRONG attraction 3.)Hydrogen Bonding (H-Bonds) - A Hydrogen atom bonded to an N, O, or F atom with a lone pair. - H-bond does NOT equate to just having a covalent bond to H, requires 2 criteria: o H-Bond Donor- H atom that is covalently bonded to N, O, or F o H-Bond Acceptor Atom- N, O, or F atom w/ one or more lone pairs - When the H bonds to an F atom (for example), the F hoards most of the electrons, leaving H essentially a “naked proton.” It is polarized to be positive, and looking for some negative loving to match up with it. It attracts the positive dipole of the nearest other F atom. - The covalent bond between the H and the original F, N, or O is way stronger than the bond of the F, N, or O and the different H. - Here is an example using H2O, a molecule we are familiar with. VALENCE BOND THEORY AND ORBITAL HYBRIDIZATION We already know many models and ways to show atoms, however, these are not always completely accuate. The VSEPR model, for example, does not show the shape of orbitals, or explain magnetic/ spectral properties. Electrons are waves and particles, not just dots, like we see with the Lewis structure. WARNING: I would start going to class, because this is some crazy level stuff that I may not do the best job of explaining completely. But, I will give a valiant effort. HYBRIDIZATION MODELS So, basically put, atoms can change their bond preferences to help them bond with other atoms. The Electron Configuration is very helpful is determining Hybridization Models, lets observe carbon for a second. [He] |↑↓ | |↑ | ↑ | | 2s 2p BUT The Lewis Dot structure is C surrounded by 4 dots, showing the idea that there are 4 equivalent covalent bonds to be made, while the EC only shows 2 bonds wanting to be made, in the 2p shell. So when bonds are trying to be made, the atom REARRANGED ITSELF to fit the bonds! For an EC in this situation, you take the number of equivalent orbitals to be made (here is 4) and make them into their “own” chart. Carbon then goes from: [He] |↑↓ | |↑ | ↑ | | 2s 2p TO |↑ |↑ |↑ |↑ | sp3 orbital One s orbital and two p orbitals combine to form a sp3 orbital with 4 equivalent bonds ready to be made. I know; crazy right? The orbital shapes combine also, to look like: The Orbitals for bonding “mix” forming 4 EQUIVALENT orbitals. The energy is now between the original energies of s and p. HYBRIDIZATION AND LEWIS STRUCTURE The Electron Config. of the Hybridization bonds will come from how many e- domains the CENTRAL atom has. Let’s look at H2O. We know that it the central atom has two lone pairs and two bonds, so it has four groups of electrons to accommodate, so 4 domains in total. One S and 3 P orbitals, so sp3 orbital. |↑↓ |↑↓ |↑ |↑ | sp3 orbital Lone PaiBonding Electrons CH3 H 4 domains on C 4 Domains on O sp3 hybridization sp3 hybridization H C OH H SF4 5 domains on S F 4 bonded F S F 1 lone pair sp3d hybridization seesaw geometry F HYBRID ORBITAL THEORY- bond type Sigma bonds have the highest amount of overlap, all single bonds are sigma bonds Pi bonds, sideway overlap of p orbitals, less strong bond but more reactive than sigma bonds DOUBLE BONDS Double bonds have one sigma overlap (end-to-end bond, stronger) and one pi overlap (side of one atom to side of another, weaker). The overall bond is shorter than one sigma bond alone, and stronger than one sigma bond alone. TRIPLE BONDS Triple bonds are formed by sp hybridized atoms, two sp hybrid orbitals and two unhybridized p orbitals. This type of bonding includes one pi bond (with two lobes) and one sigma bond. Triple are shorter and stronger than double bonds, but the pi bonds are weaker than the sigma bonds.
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