chapter 9

• molecular orbital theory uses molecular orbitals instead of atomic orbitals to model bonding
• molecular orbitals deal better with delocalized electrons, molecules with unpaired electrons, and bond energies
• molecular orbitals can be thought of as combinations and differences of the wave functions of the constituent orbitals, rather than averages like in hybridization
• molecular orbitals deal with bonding orbitals (lower energy) and anti-bonding orbitals (higher energy)
• bond order = (# of bonding electrons - # of anti bonding electrons) / 2
• homonuclear diatomic molecules are those composed of two same elements
• when two atoms bond, the valence orbitals are the ones that contribute to the molecular orbitals
• in homonuclear diatomics with only s valence orbitals, one sigma bonding orbtial and one sigma antibonding orbital form
• bonding happens when charges are the same
• antibonding happens when charges are different
• s-p mixing is where the energy levels of the s and p orbitals are mixed when creating the molecular orbitals (important for B, C, and N)
• paramagnetic = attracted to magnetic field
• in homonuclear diatomic molecules, atomic valence orbitals are degenerate and there are the same types of atomic valence orbitals
• heteronuclear diatomic molecules have different atomic valence orbitals
• effective nuclear charge (Zeff) is used to decide energy levels of the atomic valence orbitals
• atoms with a higher Zeff will have lower energy valence orbitals
• molecular orbitals are used when there are resonance structures with pi bonds