What are Quantum Numbers and what do they describe?
Quantum numbers describe size, shape, orientation, and number of atomic orbitals that an element poses.
What does the principal quantum number describe?
n = energy level (shell)
Indicates electrons distance from the nucleus
What does the azimuthal number describe?
l = subshell
0 to n-1
s p d f
What does the magnetic quantum number describe?
ml = orbital
-l to +l
shapes of those orbitals
x y z-axis
What does the spin quantum number describe?
ms = spin of an electron
plus or minus 1/2
Created by head-to-head or tail-to-tail overlap of atomic orbitals of the same sign and are energetically favored
Created by head-to-head or tail-to-tail overlap of atomic orbitals that have opposite signs
What kind of bonds do
Single bonds, Double Bonds and Triple Bonds contain?
- Single bonds are Sigma bonds which contain two electrons
- Double bonds contain one sigma bond and one pi bond (sharing of electrons between two unhybridized p-orbitals that align side by side.
- Triple bonds contain one sigma bond and two pi bonds
SP3 orbitals character
25% S Character
75% P Character
109.5 bond angles
carbons with all single bonds are sp3
SP2 hybridized orbital character
33% S Character
67% P Character
Trigonal planar geometry
120 bond angles
carbons with one double bond are sp2
Resonance describes the delocalization of electrons in molecules that have conjugated bonds
Occurs when a single and multiple bonds alternate, creating a system of unhybridized p-orbitals down the backbone of the molecule through which pi electrons can delocalize
- Resonance increases the stability of a molecule
- various resonance form all contribute to the true electron density of the molecule: the more stable resonance form, the more it contributes.
- Resonance forms are favored if they lack formal charge, form full octets on electronegative atoms, or stabilize charges through induction and aromaticity