An empirical method for estimating shielding constants and effective nuclear charge of electrons.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
Slater's rules are an empirical method for estimating the shielding constant S for each electron, and hence its effective nuclear charge. Electrons in the same ns and np group contribute 0.35 each (0.30 for 1s), electrons in the n minus 1 shell contribute 0.85 each, and electrons in deeper shells contribute 1.00 each. The method gives approximate values that are useful for understanding trends rather than exact energies. It requires careful bookkeeping of electron groups, but it is quick to apply. Slater's rules are widely used for rapid estimates.
Key ideas: Group orbitals as (1s)(2s,2p)(3s,3p)(3d)(4s,4p)... For an ns or np electron: other electrons in the same group count 0.35 (0.30 for 1s), n-1 shell electrons 0.85, lower shells 1.00. For nd or nf electrons all electrons to the left count 1.00. Then Z_eff = Z - S. Example: N valence: S = 4 x 0.35 + 2 x 0.85 = 3.10, Z_eff = 3.90.
Common mistakes and connections: Students include the electron itself in the count or use the wrong shell groupings, forgetting that electrons to the right of the group do not shield at all. The rules are approximate, written for estimating radius and ionization trends, and applied to both ground and ions.
For Na the 3s electron has Z = 11, shielding S = 8 x 0.85 + 2 x 1.00 = 8.8, so Zeff = 11 - 8.8 = 2.2. The interactive lesson shows this as a live animation or chart.
For a 4s electron in potassium, S = 8 x 0.85 + 10 x 1.00 = 16.8, so Z_eff = 19 - 16.8 = 2.2.
An empirical method for estimating shielding constants and effective nuclear charge of electrons.
Slater's Rules is a advanced topic in Atomic Structure & Periodicity. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Atomic Structure & Periodicity first: Core Electrons, Effective Nuclear Charge, Shielding Effect.
The next topics in Atomic Structure & Periodicity are Penetration of Orbitals and Periodic Law.
Yes. The interactive lesson includes a self-check question on Slater's Rules, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Slater's Rules is topic 72 of 115 in Atomic Structure & Periodicity.