1. What is Effective Nuclear Charge (Zeff)?

Effective nuclear charge (Zeff) is the net positive charge experienced by an electron in a multi-electron atom. It accounts for both the attraction to the nucleus and repulsion from other electrons.

2. How Does the Calculator Work?

The calculator uses the basic Zeff equation:

Where:

• \( Z \) — Atomic number (number of protons)
• \( S \) — Shielding constant (empirical value)

Explanation: The shielding constant represents how much the inner electrons shield the outer electrons from the nucleus.

3. Importance of Zeff Calculation

Details: Zeff helps explain periodic trends like atomic size, ionization energy, and electron affinity. Higher Zeff means electrons are held more tightly.

4. Using the Calculator

Tips: Enter the atomic number (1-118) and shielding constant (typically between 0 and Z-1). The shielding constant can be found in chemistry reference tables.

5. Frequently Asked Questions (FAQ)

Q1: How does Zeff vary across the periodic table?
A: Zeff generally increases left to right across a period and decreases down a group, though with exceptions.

Q2: What are typical Zeff values?
A: For valence electrons, Zeff ranges from about +1 to +8 for main group elements.

Q3: How is the shielding constant determined?
A: S is determined experimentally or through quantum mechanical calculations for each electron configuration.

Q4: Why is Zeff different for different electrons?
A: Inner electrons experience nearly the full nuclear charge, while outer electrons are shielded by inner ones.

Q5: How does Zeff affect chemical properties?
A: Higher Zeff means smaller atomic radius, higher ionization energy, and greater electronegativity.