(1s) (2s, 2p) (3s, 3p) (3d) (4s, 4p) (4d) (4f) (5s, 5p) (5d)… Fill the electrons according to Aufbau principle. Any electrons to the right of the electron of interest do not contribute to shielding constant. The shielding constant for each group is formed as the sum of the following contributions: Each other electron in the same group as the electron of interest shield to an extent of 0. 35 nuclear charge units except 1s group, in which the other electron contributes only 0. 30. If the group (n) is of [s, p] type, an amount of 0. 85 from each electron in (n-1)th shell and an amount of 1. 00 for each electron from (n-2) and lower shells is added to the shielding constant. If the group is of [d] or [f] type, an amount of 1. 00 for each electron from all lying left to that orbital.
Electronic configuration- (1s2) (2s2, 2p3). Screening constant, σ = (0. 35 × 4) + (0. 85 × 2) = 3. 10 Effective nuclear charge, Z* = Z – σ = 7 – 3. 10 = 3. 90
Electronic configuration- (1s2) (2s2, 2p6)(3s2, 3p2). σ = (0. 35 × 3) + (0. 85 × 8) + (1 × 2) = 9. 85 Z* = Z – σ = 14 – 9. 85 = 4. 15
Electronic configuration- (1s2) (2s2, 2p6)(3s2, 3p6)(3d10)(4s2). For 4s electron, σ = (0. 35 × 1) + (0. 85 × 18) + (1 × 10) = 25. 65 Z* = Z – σ = 30 – 25. 65 = 4. 35 For 3d electron, σ = (0. 35 × 9) + (1 × 18) = 21. 15 Z* = Z – σ = 30 – 21. 15 = 8. 85
Electronic configuration- (1s2) (2s2, 2p6)(3s2, 3p6)(4s2, 4p6) (3d10) (4f14) (5s2, 5p6)(5d4), (6s2) σ = (0. 35 × 1) + (0. 85 × 12) + (1 × 60) = 70. 55 Z* = Z – σ = 74 – 70. 55 =3. 45
