W2013CHM2311 Part 4b Notes

symmetry considera0ons for of 2py 2px 2pz energy 159

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Unformatted text preview: ΔE ϕ2 ψMO= c1ϕ1 + c2ϕ2 in- phase (bonding) interac0on Energies of Atomic Orbitals and Orbital Interac0ons In heteronuclear diatomics, each of the atomic orbitals makes a different contribuBon to the molecular orbitals. out- of- phase (an0bonding) interac0on ψ*MO = c2ϕ1 – c1ϕ2 The closer ϕ2 and ϕ1 are in energy, the closer the MO is to a homonuclear diatomic. Energy ΔE’ ϕ1 ΔE ϕ2 ψMO= c1ϕ1 + c2ϕ2 in- phase (bonding) interac0on ↳  If E (ϕ2) = E (ϕ1), then c1 = c2, the equa0on reduces to the equa0on for homonuclear diatomics. Energies of Atomic Orbitals and Orbital Interac0ons The farther apart ϕ2 and ϕ1 are in energy, the more non- bonding the molecular orbitals are. ↳  As a general rule, if E (ϕ2) – E (ϕ1) > 13 eV , then c1 (or c2) is equal to 0. ↳  i.e., no interac0on between atomic orbitals occurs. ψ*MO = c2ϕ1 – c1ϕ2 ψ*MO = ϕ1 ϕ1 >13eV ϕ2 ψMO= c1ϕ1 + c2ϕ2 Energy Energy ϕ1 >13eV ψMO= ϕ2 ϕ2 Nonbonding Orbitals When an atomic orbital does NOT interact with any other atomic orbital, it is called a nonbonding molecular orbital. The orbital retains the same shape and energy in the molecule as it had in the isolated atom. ψ*MO = ϕ1 Energy ϕ1 >13eV ψMO= ϕ2 ϕ2 Energies of Atomic Orbitals and Orbital Interac0ons In heteronuclear diatomics, since each of the atomic orbitals makes a different contribuBon to the molecular orbitals, each molecular orbital will be more similar in appearance to the atomic orbital that has the greatest contribu0on to it. ↳  i.e. is closest to it in energy ψ*MO = c2ϕ1 – c1ϕ2 ΔE’ Energy ϕ1 ΔE ψMO= c1ϕ1 + c2ϕ2 ϕ2 Deriving Molecular Orbital Diagrams of Heteronuclear Diatomics Example: O...
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