W2013CHM2311 Part 4b Notes

4 to dis0nguish between orbitals they are given

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Unformatted text preview: atoms Heteronuclear diatomic molecules are molecules containing two atoms of different elements. e.g. CO, HF Heteronuclear diatomics have a similar bonding pacern as homonuclear diatomics, except atomic orbitals on the two atoms are NOT iden0cal. MO Diagram for CO Carbon Monoxide: Both carbon and oxygen are in the second period so only need to consider the 2s and 2p orbitals for each atom. Recall the three factors that are important in the MO approach are: 1. Symmetry of atomic orbitals. 2. Rela0ve energies of atomic orbitals. 3. Distance between atoms (must overlap). If we consult the table of valence orbital potenBal energies we find following data. C (2s) = - 19.5 eV O (2s) = - 32.4 eV C (2p) = - 10.7 eV O (2p) = - 15.9 eV For each case, the orbital from oxygen has the lower energy (larger negaBve number). MO Diagrams for N2 vs. CO CO is isoelectronic with N2. The MOs of CO will be of σ or π symmetry but will not exhibit any g or u dependence. 2p energy σu * πg* πg* 2p 2p 2p πu πu σg 2s σu * 2s 2s σg N2 C 2s O MO Diagram for CO Some differences from homonuclear diatomics: 2π* 2π* 2p 1.  Atomic orbitals on different atoms have different energies. ↳  e.g., carbon 2s and oxygen 2s 3.  Molecular orbitals are no longer given “g” and “u” symmetry labels due to distor0on in their shapes. 4.  To dis0nguish between orbitals, they are given numbers. The lowest energy σ is 1, the next is 2, etc. Other numbering systems are also frequently used. 3σ 2p energy 2....
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This note was uploaded on 03/28/2014 for the course CHM 2311 taught by Professor Richardson during the Winter '09 term at University of Ottawa.

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