How to Determine Screening Constant and Effective Nuclear Charge
Write down the electronic configuration of the element as shown below., For example: (a) Calculate effective nuclear charge in Nitrogen for 2p electron., (b) Calculate effective nuclear charge and screening constant seen in 3p electron in Silicon...
Step-by-Step Guide
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Step 1: Write down the electronic configuration of the element as shown below.
(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:
All other electrons in the same group as the electron of interest shield to an extent of
0.35 nuclear charge units except 1s group, where the other electron contributes only
0.30.
If the group is of the type, an amount of
0.85 from each electron (n-1) shell and an amount of
1.00 for each electron from (n-2) and lower shell.
If the group is of the or type then an amount of
1.00 for each electron from all lying left to that orbital. -
Step 2: For example: (a) Calculate effective nuclear charge in Nitrogen for 2p electron.
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 , (At.
No. =74) 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 -
Step 3: (b) Calculate effective nuclear charge and screening constant seen in 3p electron in Silicon.
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Step 4: (c) Calculate effective nuclear charge in Zinc for 4s electron & for 3d electron.
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Step 5: (d) Calculate effective nuclear charge on one of 6s electron in tungsten.
Detailed Guide
(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:
All other electrons in the same group as the electron of interest shield to an extent of
0.35 nuclear charge units except 1s group, where the other electron contributes only
0.30.
If the group is of the type, an amount of
0.85 from each electron (n-1) shell and an amount of
1.00 for each electron from (n-2) and lower shell.
If the group is of the or type then 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 , (At.
No. =74) 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
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Evelyn Hayes
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