1. What is Effective Nuclear Charge?

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

Where Z is the atomic number and σ is the screening constant.

2. How Does the Calculator Work?

The calculator uses the simple Zeff equation:

Where:

• \( Z \) — Atomic number (number of protons)
• \( \sigma \) — Screening constant (accounts for electron shielding)

Explanation: The equation shows that the effective nuclear charge is the actual nuclear charge reduced by the shielding effect of other electrons.

3. Importance of Zeff Calculation

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

4. Using the Calculator

Tips: Enter the atomic number (1-118) and the screening constant (typically between 0 and Z-1). The screening constant can be estimated using Slater's rules.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for Zeff?
A: For valence electrons, Zeff ranges from +1 to +8 for main group elements.

Q2: How does Zeff vary across the periodic table?
A: Zeff increases across a period (left to right) and remains relatively constant down a group.

Q3: What are Slater's rules?
A: Empirical rules to estimate the screening constant σ based on electron configuration.

Q4: Why is Zeff important in chemistry?
A: It explains why atoms get smaller across a period (higher Zeff pulls electrons closer) and why ionization energy increases across a period.

Q5: How accurate is this simple calculation?
A: It provides a basic estimate. More sophisticated calculations consider electron probability distributions.