Slater rule with example ~ NEET chemistry

This rule help us to predict the sceening constant and effectively nuclear charge(Zeffect) in the atom.

Screening contant is denoted by sigma.
Effective nuclear charge is denoted by (Zeffect)

Zeffect = Z-sigma

:. Z = atomic number

Sigma = screening constant

Order to calculate the screening constant in the atom following steps are :---

First we write the Electronic configuration of that atom.
Then for the goven shape we construct The shape of energy level for a given shell.

(s p), (d), (f)

S and p have almost same energy. Thats why Both shell consider together.

For example :---

Nitrogen :-- (1s²)(2s² 2p³)

Chromium :--(1s²)(2s² 2p6)(3s² 3p6)(3d5)(4s¹)

3. Then calculate sigma for ns and np electron.

(a) electron in the same ns and np orbital contribute 0.35 each, for the calculation of sigma, for 1s orbital 0.30 works better.

(b) electron in the (n-1) shape contribute 0.85 each.

(c) electron in the (n-2), (n-3) or lower shell contribute 1.0 each.

(4) calculation of sigma for nd and nf electrons.

(a) electron in nd and nf orbitals contribute 0.35 each.

(b) electron in the remaining orbitals contribute 1.0 each.

Quest. :-- calculate the screening constant and effective nuclear charge for element oxygen?

Soln. :-- Oxygen = ( 1s²)(2s²2p4)

1s²= (n-1) sub shell

2s² 2p4= ns and np sub shell

Sigma = 5*0.35+2*0.85

= 1.75+1.70

= 3.45

Zeffect = Z-sigma

=8-3.45 (oxygen atomic no is 8)

4.55

Ques.:-- calculate the sigma and Zeffect in Cu for. :--

(a) 4s. (b) 3d. (c) 3p. (d) 3p

(e) 3s. (f) 1s. (g) incoming electron

Soln. :-- Cu = (1s²)(2s² 2p6)(3s² 3p6 3d10)(4s1)

1s = (n-3) subshell

2s 2p = (n-2) subshell

3s 3p.3d = (n-1) subshell

4s = n subshell

(a) 4s. = (0*0.35)+(18*0.85)+(8*1)+(2*1)

= 15.30+8+2

= 25.20

Zeffect = 29-25.20

= 3.70

(b) 3d = (9*0.35)+(8*1)+(8*1)+(2*1)

=3.15+8+8+2

=21.15

Zeffect = 29-21.15

= 7.85

= 2.45+6.80+2

= 11.25

Zeffect = 29-11.25

=17.75

(d) 2p = 7*0.35+2*085

= 2.45+1.70

= 4.15

Zeffect = 29-4.15

= 24.85

(e) 3s = same as 3p

(f) 1s = 1*0.35

= 0.30

Zeffect =29-0.30

= 28.70

(g) incoming electron = 1*0.35+18*0.85+8*1+2*1=0.35+15.30+8+2

= 25.75

Zeffect = 29-25.75

= 3.25

Atomic no of copper is 29

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