E

Effective Nuclear Charge

Z_eff = Z − σ (Slater's rules)
Quick Reference
Formula / NotationZ_eff = Z − σ (Slater's rules)
Also Known AsZ_eff; net nuclear charge; screened nuclear charge; shielded nuclear charge; Slater Z_eff

What is Effective Nuclear Charge?

Effective nuclear charge (Z_eff) is the net positive charge experienced by an electron in a multi-electron atom, after accounting for the shielding (screening) effect of other electrons. It is always less than the actual nuclear charge Z because inner-shell electrons partially shield outer electrons from the full nuclear attraction. Z_eff increases across a period and is approximately constant down a group.

Formula & Notation

Z_eff = Z − σ (Slater's rules)

Other Names / Synonyms: Z_eff; net nuclear charge; screened nuclear charge; shielded nuclear charge; Slater Z_eff

Properties & Characteristics

Z_eff = Z − σ (where σ = shielding constant); calculated using Slater's rules; increases left to right across a period; approximately constant down a group; determines atomic radius, ionisation energy, and electronegativity trends; inner electrons shield more effectively than outer electrons

Uses & Applications

Explaining periodic trends (atomic radius, ionisation energy, electronegativity); understanding why elements across a period become smaller; predicting chemical reactivity; quantum chemistry calculations

Safety Information

No hazard — a theoretical atomic property.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Effective Nuclear Charge
Formula Z_eff = Z − σ (Slater's rules)
Synonyms Z_eff; net nuclear charge; screened nuclear charge; shielded nuclear charge; Slater Z_eff

Frequently Asked Questions

Effective nuclear charge (Z_eff) is the net positive charge experienced by an electron in a multi-electron atom, after accounting for the shielding (screening) effect of other electrons. It is always less than the actual nuclear charge Z because inner-shell electrons partially shield outer electrons from the full nuclear attraction. Z_eff increases across a period and is approximately constant down a group.

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