Chemistry 30A
Chem 30A Ch.1-4: Condensed Chang’s Class Notes
Chapter 1
Valence electrons octet rule exceptions P and S can have 10 or 12 valence e-
B and Al (Group 3) can have 6 valence e- electronegativity- how much an atom wants e-
< 0.5 = nonpolar, covalent (i.e. H2)
0.5 - 1.9 = polar covalent direction of polarity (using arrow and delta symbol) overall dipole
> 1.9 = ionic formation of ions fish-hook arrow
Lewis structure formal charge
Functional Groups
Molecular Shape
VSEPR (Valence Shell e- Pair Repulsion) bonds contain e- (negative) these repel one another sp3 i.e. CH4
4 regions of e- tetrahedral 109.5°
25% s-character, 75% p-character sp2 i.e. CH2O
3 regions of e- trigonal planar
120°
33% s-character, 66% p-character sp i.e. CO2
2 regions of e- linear 180°
50% s-character, 50% p-character
Orbitals
Einstein: photoelectric effect → photons de Broglie → wave-particle duality
Schrodinger → wave functions ?→ orbitals
Atomic orbitals
Simple Molecular Orbital Theory
# MO’s = #AO’s
MO’s arranged by relative E
Filling follows (1: Aufbau, 2: Pauli)
Bond Order
(e- in bonding orbital - e- in antibonding) / 2
Valence Bond Theory places e- pairs between atoms problems incorrect bond geometry energy C-H 101 kcal/mol
2s + 1s H
2px + 1s H
2py + 1s H
2pz + 1s H
Hybridization
look over diagrams in notes/book
Combined MO + VB Theory
MO = bonding/antibonding
VB = hybridization look over diagrams in notes/book
ON MIDTERM: “Draw full combined valence bond/molecular orbital bonding picture “ in NOTES try these:
CH3--C ≡ N
CO2
Resonance arrow movement formal charge brackets double-headed arrow hybridization greater contributing structure? filled valences more covalent bonds minimize charge separation charges on atoms of appropriate EN
NOTE: Hybrid looks like major contributor
ON MIDTERM
TRY THESE:
CH3N3
O3
CH3CO2
Chapter 2
Saturated alkanes: maximum of C-H bonds
Representations
ball + stick
line
Chapter 1
Valence electrons octet rule exceptions P and S can have 10 or 12 valence e-
B and Al (Group 3) can have 6 valence e- electronegativity- how much an atom wants e-
< 0.5 = nonpolar, covalent (i.e. H2)
0.5 - 1.9 = polar covalent direction of polarity (using arrow and delta symbol) overall dipole
> 1.9 = ionic formation of ions fish-hook arrow
Lewis structure formal charge
Functional Groups
Molecular Shape
VSEPR (Valence Shell e- Pair Repulsion) bonds contain e- (negative) these repel one another sp3 i.e. CH4
4 regions of e- tetrahedral 109.5°
25% s-character, 75% p-character sp2 i.e. CH2O
3 regions of e- trigonal planar
120°
33% s-character, 66% p-character sp i.e. CO2
2 regions of e- linear 180°
50% s-character, 50% p-character
Orbitals
Einstein: photoelectric effect → photons de Broglie → wave-particle duality
Schrodinger → wave functions ?→ orbitals
Atomic orbitals
Simple Molecular Orbital Theory
# MO’s = #AO’s
MO’s arranged by relative E
Filling follows (1: Aufbau, 2: Pauli)
Bond Order
(e- in bonding orbital - e- in antibonding) / 2
Valence Bond Theory places e- pairs between atoms problems incorrect bond geometry energy C-H 101 kcal/mol
2s + 1s H
2px + 1s H
2py + 1s H
2pz + 1s H
Hybridization
look over diagrams in notes/book
Combined MO + VB Theory
MO = bonding/antibonding
VB = hybridization look over diagrams in notes/book
ON MIDTERM: “Draw full combined valence bond/molecular orbital bonding picture “ in NOTES try these:
CH3--C ≡ N
CO2
Resonance arrow movement formal charge brackets double-headed arrow hybridization greater contributing structure? filled valences more covalent bonds minimize charge separation charges on atoms of appropriate EN
NOTE: Hybrid looks like major contributor
ON MIDTERM
TRY THESE:
CH3N3
O3
CH3CO2
Chapter 2
Saturated alkanes: maximum of C-H bonds
Representations
ball + stick
line