1) Using Slater’s rule confirm that the experimentally observed electronic
configuration of K, 1s2 2s2 2p6 3s2 3p6 4s1, is energetically more stable than the
configuration 1s2 2s2 2p6 3s2 3p6 3d1.
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
Tutorial – 3 (Group X)
2) Use Slater’s rules to estimate values of Zeff for (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 1s22s22p4
respectively. 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.
Tutorial – 3 (Group X)
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+.