How to Calculate Effective Nuclear Charge (Zeff)
Calculate electron shielding and net atomic attraction:
Enter Atomic Number (Z)
Input the total positive nuclear charge (number of protons Z).
Count Same-Shell Electrons
Count remaining electrons in the target electron's principal quantum group (each contributes 0.35 shielding).
Count Inner-Shell Electrons
Count core electrons in (n-1) and deeper shells (contributing 0.85 and 1.00 shielding).
Compute Zeff = Z - S
Subtract calculated shielding constant S from Z to find net effective nuclear pull.
Key Features & Slater Parameters
Slater's Shielding Weights
Implements standard 0.35, 0.85, and 1.00 empirical shielding constants.
Periodic Trend Explanations
Explains why atomic radius decreases across a period as Zeff increases.
Instant Visual Breakdown
Clear mathematical contribution from each electron shell.
Periodic Trends Guide: Effective Nuclear Charge & Shielding
In multi-electron atoms, valence electrons do not experience the full electrostatic pull of the positive nuclear charge because intervening inner-shell electrons push outward via electrostatic electron-electron repulsion. This reduction in nuclear pull is termed electron shielding.
The net pull experienced by a valence electron is called the effective nuclear charge (Zeff), expressed by:Zeff = Z - Swhere Z is the atomic number and S is the shielding constant derived from Slater's Rules.
Frequently Asked Questions
?How does Zeff change across a period in the periodic table?
Zeff increases moving left-to-right across a period because protons (Z) increase by 1 while same-shell valence electrons shield poorly (0.35 each), pulling electrons closer and decreasing atomic radius.