1. What is Effective Nuclear Charge?

Effective nuclear charge (Zeff) is the net positive charge experienced by an electron in a multi-electron atom. The term "effective" is used because the shielding effect of negatively charged electrons prevents higher orbital electrons from experiencing the full nuclear charge.

2. How Does the Calculator Work?

The calculator uses the simple Zeff equation:

Where:

• \( Z \) — Atomic number (number of protons in nucleus)
• \( \sigma \) — Shielding constant (number of core electrons)

Explanation: Core electrons shield the valence electrons from the full charge of the nucleus. This simplified calculation works well for main group elements.

3. Importance of Zeff Calculation

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

4. Using the Calculator

Tips: Enter the atomic number (1-118) and number of core electrons (inner-shell electrons that shield the valence electrons).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between Z and Zeff?
A: Z is the actual nuclear charge (number of protons), while Zeff is the net charge experienced by an electron after accounting for shielding.

Q2: How do I find the number of core electrons?
A: Core electrons are all electrons not in the outermost shell. For main group elements, it's the total electrons minus the group number.

Q3: Why does Zeff increase across a period?
A: While protons are added, shielding increases only slightly as electrons are added to the same shell, resulting in higher effective nuclear charge.

Q4: What are typical Zeff values?
A: For valence electrons, Zeff ranges from about +1 to +8 for elements in periods 2-6.

Q5: Are there more accurate methods?
A: Yes, Slater's rules provide a more sophisticated approach to calculating shielding constants.