Lecture 9 9/24/2024 If 1s e-s were not there, 2s and 2p would have same E 4s < 3d (for K, Ca, etc.) larger n value, less penetration (a bit very difficult to "see" nucleus) 4s is 2s... e-'s in 3d closer to nucleus than 4s but blocked from nucleus. if 3d is closer, why is 4s lower in E? e-'s in 4s can penetrate and get thru screening e-'s, spending a little more time closer to the nucleus 4s VE so much < 3d momentarily. 3d does not drop in E like 4s as: ↓ penetration thru screening e-'s 4s goes below 3d at K - first point where 4sE < 3dE 4s not always below 3d (4s > 3d in all transition metals in molecules), essentially seen as equal wait 2 n levels to fill neutral: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p cations: 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 3d, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p lower n fills first shielding issue lessened b/c e-'s moved out to make cations. Cation Strategy count up # of valence e-'s in neutral Subtract the # of e-'s needed to make cation order them according to cation orbitals find e- configurations: Ti: 22 e, 4 val. go to core (Ar), then add 4s² and predict 3d² Ti: (Ar) 4s² 3d² go according to cation ordering - 2e- in 3d Ca: 20e, 2 val. (Ar) 4s²; acc. to neutral order Mo: 42e, 2 val. (Kr) core, neutral has 0 val e-, subtract 4 -> 2e- in 4d Mo: (Kr) 5s² 4d⁴ (prediction be. Hund's rule falls apart later in P.T) Am: 95e, 8 val. (Rn) 5f⁶ 6d¹ 7s² (9-3=6 in 5f) Os: 76e, 8 val. (Xe) 6s² 4f¹⁴ 5d⁶ (once 5d all full, 14f -> back to 6s) Tl: 81e, 3 val. (Xe) 6s² 4f¹⁴ 5d¹⁰ 6p¹ (considered part of core once full; val = 6s¹ 6p¹ 6d¹ is also val) 4f, 5d, 6p approx. val. es = anything past noble gas config. if a subshell has not filled correctly (ex. very delayed n=4 subshell), it is no longer considered part of valence shell in level. usually d or f that hasn't filled yet but of previous n level much closer to nucleus -> not involved in bonding