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Effective nuclear charge, Z eff = Z  S

1 ) Using Slater’s rule confirm that the experimentally observed electronic configuration of K, 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 , is energetically more stable than the configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 1 . Slater’s rule:.

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Effective nuclear charge, Z eff = Z  S

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  1. 1) Using Slater’s rule confirm that the experimentally observed electronic configuration of K, 1s2 2s2 2p6 3s2 3p64s1, is energetically more stable than the configuration 1s2 2s2 2p6 3s2 3p63d1. Slater’s rule: The electron at the r radius experiences a repulsion from the total charge within the sphere of radius r; charge outside that radius has no net effect. Effective nuclear charge, Zeff = Z  S Z = nuclear charge S = shielding or screening constant • Consider a particular electron in an ns or np orbital: • Each of the other electrons in the (ns, np) group contributes S = 0.35 • Each of the electrons in the (n-1) shell contributes S = 0.85 • Each of the electrons in the (n-2) or lower shells contributes S = 1.00 • Consider a particular electron in an nd or nf orbital: • Each of the other electrons in the (nd, nf) group contributes S = 0.35 • Each of the electrons in a lower group than the one being considered contributes S = 1.00

  2. Tutorial – 3 (Group X) 2) Use Slater’s rules to estimate values of Zefffor (a) a 4s and (b) a 3d electron in a V atom. From above estimates, explain why the valence configuration of the ground state of a V+ ion is likely to be 3d34s1 rather than 3d24s2. 3) Assume three p-block elements A (Z = 6), B (Z = 7) and C (Z = 8) having ground state electronic configuration 1s22s22p2 ,1s22s22p3 and 1s22s22p4respectively. The increase in Zeff between A and B is 0.69 whereas the increase between B and C is only 0.62. Suggest a reason why the increase in Zeff for a 2p electron is smaller between B and C than between A and B given the configurations of the atoms listed above.

  3. Tutorial – 3 (Group X)

  4. Tutorial – 3 (Group X) 4) Explain why the first ionization energy of phosphorus, P (I1=1011 kJ/mol) is more than sulfur, S (I1=1000 kJ/mol). 5) Predict the ground-state electron configurations of (a) Ti and (b) Ti3+.

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