lecture 8 9/19/2024 Orbital Questions (Page 1): how many of orbitals (l=3) are available in a hydrogen atom? 8 how many possible values of ml: l=3 (-3,-2,-1,0,1,2,3) how many radial nodes does a 6f orbital have? 5 total nodes, 3 angular, 2 radial 4f: 6g : 4f orbital 45, 90, 135 diagram of an f orbital shown with radial and angular nodes. Additional Notes (Page 1): magnetic moment: an e- can interact with a magnetic field in two ways (spin) +1/2 (up) or -1/2 (down) aufbau principle a multi-electron atom can be approximated as a superposition of electrons in H-like atoms repulsion; attraction each e- has a unique set of quantum #s (Pauli) ASSUME electrons do not know of each other's existence in an atom an atom’s E is to be as low as possible Hund's Rules: orbitals fill according to value of (n+l) ; lowest (n+l) possible for a given (n+l) : low n fills first orbitals in a subshell are singly occupied when possible e- spins tend to line up when possible exclusion principle: forbids e’s from doing certain things according to quantum mechanics hund's rules: guidelines to predict the most stable atom predicted order of orbitals: 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 1 2 2 3 4 4 5 5 6 6 6 7 7 7 8 8 8 n+l Energy Levels Diagram and Notes (Page 2): Energy Diagram shown, with 1s lowest, with 2s and 2p slightly overlapping, with e- filling each. diagram of E levels Li: [He]2s1 Be: [He]2s2 B: [He]2s2 2p1 C: [He]2s2 2p2 N: [He]2s2 2p3 O: [He]2s2 2p4 F: [He]2s2 2p5 Ne: [He]2s2 2p6 2s and 2p = E in H atom Li valence e- at much ↑E than He; easier to remove ( ionization/binding E) IE: amount of E it costs to remove an e- as much E to get out; not as deep in potential well higher in diagram, easier to remove e- even if Be has a greater nuclear charge than Li, it's E is higher due to e- repulsion within the same orbital degenerate orbitals: diff. orbitals of same E easier to remove an e- from O than N bc e-'s paired competing factors: ↑ nuclear charge (↓E) and e- repulsion (↑E) which wins depends on nuclear charge and n diagram comparing 1s, 2s, and 2p orbitals in electron shielding. Electron Shielding Section (Page 2): electron shielding 2s < 2p 1s : less "blocking" effect than with 2p bc some prob. of 2s being close to nucleus > e- in 2s than 2p inner shell shield outer not as much attraction felt -> ↓ E ↑ e- repulsion diagrams included for 1s, 2s and 2p orbitals with the relative position to the nucleus. average position the same for same n level e-'s in 1s orbital are in the way of 2s e-'s "seeing" the nucleus

CHEM 1810 - Lecture 8

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