Slater’s rules & shielding. e- further out, are shielded by e- closer to the nucleus, thus reducing attraction of far e- and nucleus. e- feel a Z*effective < Ztrue Due to shielding effects, simple order of orbital fill up (1s2s2p…) holds only at very low atomic #’s Shielding effects force orbital overlap & 4s fill up before 3d. Slater’s rule are rough (approximations), guide to determine shielding. Z* - measure of the nuclear attraction of e- Z* = Znuclear charge – Sslater’s consant RULES: 1) Electron structure of an atom is written in groupings: a. Such as (1s)(2s,2p)(3s,3p)(3d)(4s,4p)(4d)(4f)(5s,5p)etc… 2) e- in higher groups (to the right)do not shield those in lower groups. 3) For ns or np valence e-: a. e- in the same ns, np group contribute 0.35 [ except 1s, where they contribute 0.30 ] b. e- in n-1 group contribute 0.85 c. e- in n-2 group contribute 1.00 4) For nd and nf valence e-: a. e- in the same nd or nf group contribute 0.35 b. e- in groups to the left contribute 1.00
Posted on: Sat, 27 Jul 2013 11:21:33 +0000