Question

In Slater's rules, electrons in the same group as your electron of interest count for 0.35 units of shielding. Explain how an electron in the same subshell is able to contribute to shielding. Aren't they the same distance from the nucleus?

Answer 1

Slater's rules allow you to estimate the effective nuclear charge Zeff from the real number of protons in the nucleus and the effective shielding of electrons in each orbital "shell" (e.g., to compare the effective nuclear charge and shielding 3d and 4s in transition metals). Slater's rules are fairly simple and produce fairly accurate predictions of things like the electronic configurations and ionization energies.

Step 1 : Write the electron configuration of the atom in the following form:

(1s) (2s, 2p) (3s, 3p) (3d) (4s, 4p) (4d) (4f) (5s, 5p) . . .

Step 2: Identify the electron of interest, and ignore all electrons in higher groups (to the right in the list from Step (1). These do not shield electrons in lower groups

Step 3: Slater's Rules is now broken into two cases:

• the shielding experienced by an s- or p- electron, and
• the shielding experienced by a d- or f- electron.

s- and p-orbital Electrons

For ns or np valence electrons

1. electrons within same group shield 0.35, except the 1s which shield 0.30
2. electrons within the n-1 group shield 0.85
3. electrons within the n-2 or lower groups shield 1.00