click below
click below
Normal Size Small Size show me how
MCAT Org. Chem Ch. 3
Question | Answer |
---|---|
Quantum Numbers | Describe the size, shape, orientation, and nnumber of atomic orbitals that an element possesses |
Principal Quantum Number, n | Describes the energy level (shell) in which an electron resides and indicates the distance from the nucleus to the electron. Its possible values range from 1 to inf. |
Azimuthal Quantum Number, l | Determines the subshell in which an electron resides. Possible values range from 0 to n-1. Subshell indicated with a letter: l = 0 means s, 1 = p, 2 = d, 3 = f |
Magnetic Quantum Number, ml | Determines the orbital in which an electron resides. Possible values range from -l to l. Different orbitals have different shapes: s-orbitals are spherical, while p-orbitals are dumbbell-shaped and located on the x-, y-, or z-axis |
Spin Quantum Number, ms | Describes the spin of an electron. Possible values = +1/2 |
Bonding Orbitals | Created by head-to-head or tail-to-tail overlap of atomic orbitals of the same sign and are energetically favorable. |
Antibonding Orbitals | Created by head-to-head or tail-to-tail overlap of atomic orbitals that have opposite signs and are energetically unfavorable. |
Single Bonds | Sigma bonds which contain two electrons. |
Double Bonds | Contain one sigma bond and one pi bond. Pi bonds are created by sharing electrons between two unhybridized p-orbitals that align side-by-side. |
Triple Bonds | Contain one sigma bond and two pi bonds. |
Note About Flexibility of Multiple Bonds vs. Single Bonds | Multiple bonds are less flexible because rotation is not permitted in the prescence of a pi bond. |
Strength of Multiple Bonds vs. Single Bonds | Multiple bonds are shorter and stronger. |
Strength of Individual Pi and Sigma Bonds | Individual pi bonds are weaker than sigma bonds. |
sp3-hybridized orbitals | Orbitals that have 25% s character and 75% p character. They form tetrahedral geometry with 109.5 degree bond angles. Carbons with all single bonds are sp3-hybridized. |
sp2-hybridized orbitals | Orbitals have 33% s character and 67% p character. They form trigonal planar geometry with 120 degree bond angles. Carbons with one double bond are sp2-hybridized. |
sp-hybridized orbitals | Orbitals that have 50% s character and 50% p character. They form linear geometry with 180% bond angles. Carbons with a triple bond, or with two double bonds, are sp-hybridized. |
Resonance | Delocalization of electrons in molecules that have conjugated bonds |
Conjugation | Occurs when single and multiple bonds alternate, creating a system of unhybridized p-orbitals down the backbone of the molecule through with pi electrons can delocalize. |
Note About Resonance And Stability Of A Molecule | Resonance increases the stability of a molecule |
Note About Electron Density And Stability Of Resonant Molecule Forms | The more stable the resonance form, the more the molecule contributes electrons. |
Note About Which Resonant Forms Are Favored | Favored forms are ones that lack formal charge, form full octets on electronegative atoms, or stabilize charges through induction and aromaticity. |