Quiz #1 Flashcards
Definition of molecular orbital
Combined atomic orbitals
Molecular orbitals
Cannot be created or destroyed
Arranged in order of increasing energies
Filled according to Aufbau, Pauli, and Hund rules
Which orbital has the highest energy, bonding/sigma or antiboding/sigma*
The antibonding/sigma* orbital
This is why the bonding/sigma orbital is favored, it has the lower energy
Bonding angle and geometry for sp3 orbitals
~109.5, tetrahedral
Bonding angle and geometry for sp2 orbitals
120, trigonal planar
Bonding angle and geometry for sp orbitals
180, linear
4 regions of electron density
sp3 hybridized bonding orbital
3 regions of electron density
sp2 hybridized bonding orbital
2 regions of electron density
sp hybridized bonding orbital
Formal charge equation
of valence electrons in the neutral unbonded atom – (the # of non-bonding electrons + the # of bonds)
Rules for arrow pushing
- Double headed curved arrow means two electrons are moving
- Arrows move from electron rich regions to electron poor regions, never the other way around
Steps to drawing resonance structutes
- Convert any lone pairs to pi bonds
- Convert any pi bonds to lone pairs
- Convert any pi bonds to other pi bonds
Remember the two commandments: thou shalt not break single bonds, and thou shalt not break the octet rule for second row elements
Patters to drawing resonance structures
- Lone pair next to pi bond
- Lone pair next to C+
- Pi bond next to C+
- Pi bond between two atoms, one of which is electronegative
- Pi bonds around in a ring
What makes a valid resonance structure?
- Must have the same # of valence electrons
- Must be a valid Lewis structure
- Must have the same # of paired and unpaired electrons
Criteria for more favored resonance structures
Most filled valence shells and complete octets
Most covalent bonds
Fewest formal charges
Optimal charge distribution, with the negative charge on the most electronegative atom
Note that equally favored structures contribute equally to the resonance hybrid
