Lone atom lone atom p* s 2p 2p Use this diagram for N2 and earlier in PT p s* 2s 2s s s* 1s 1s sġ6 Taking a look at heteronuclear diatomic moleculesġ7 Taking a look at heteronuclear diatomic moleculesġ8 MOs of HF Unoccupied, E = -0.124 eV Occupied, E = -0.3523 auġ9 MOs of HF H atom F atom H – F molecule s 1s p 2p s 2s 1sĬonsidering complexity of the calculations we’ve been doing, certainly, using computers to do these calcs should be useful Computational Chemistry For polyatomic molecules can make LCAOs yMO = S ciyi - Yi constitute basis set (computational forms of atomic orbitals) Use variation theory to find ci To find structure of molecule, must move nuclei and find MOs find structure with lowest overall energy Atkins, Fig 14.30ġ5 MO Energy Level Diagram for Homonuclear Diatomics (N2 and “before”) Early, in the period, then, this permits mixing of 2s and 2pz orbitals. As you move to the right on PT, 2s and 2p energy gap increases. The sigma orbitals that we thought of as being made by the 2s orbitals are lowered in E while the sigma orbitals that we thought of as being made by the 2pz orbitals are raised in E. Molecular Orbitals not always so “clear-cut” Remember how orbitals change energy as go across PT Can affect MO energy pattern tooġ4 MO Energy Level Diagram for Homonuclear DiatomicsĮssentially LCAOs involving four orbitals are made. Remember sigma-star orbs: From s orbitals From p orbitals Remember pi-star orbs: From px orbitals From py orbitalsĭL = 0, +1, -1 DS = 0 note S = Ms note W refers to spin-orbit coupling and W = L + S DW = 0, +1, -1 Remember sigma orbs: From s orbs From pz orbs Remember pi orbs: From px orbs From py orbs Symbol is 2S + 1 L g/u 2S + 1 is multiplicity as already used for atomic term symbols g or u identifies overall parity To determine overall parity, make use of multiplication of symmetric and antisymmetric functions If the term is a S term, a right superscript of + or – is added to indicate whether the wavefunction is symmetric or antisymmetric with respect to reflection through a plane containing the two nuclei ML = S (over all e-) l l identifies “z-component” of angular momentum of an e- Symbols used to id l | l | 1 2 3 4 s p d f gĪngular momentum about “z-axis” for all electrons is L = |ML| Symbol used to id L L 1 2 3 4 S P D F G Lone atom s* lone atom p* 2p 2p p s s* 2s 2s s s* 1s 1s s Parity represents center of inversion Gerade = symmetric with inversion inversion Ungerade = antisymmetric with inversion inversionĦ MO Energy Level Diagram for Homonuclear Diatomics Px+ px OR py + py px - px OR py - py pz - pz pz + pz MOs created from combinations of p-orbitals pxA + pxB, pyA + pyB pxA - pxB, pyA - pyB pzA - pzB pzA + pzB
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |