Free Ionization Energy Calculator
Estimate the ionization energy of an atom using the hydrogen-like approximation IE ≈ 13.6 × Z_eff² / n² eV, from effective nuclear charge and principal quantum number.
Ionization Energy
7.31 eV
Ionization Energy706 kJ/mol
Ionization Energy vs Effective Nuclear Charge (Z_eff)
Ionization Energy Estimation
Formula
IE ≈ 13.6 × Z_eff² / n² (eV)
Where:
To convert eV to kJ/mol, multiply by 96.485.
Ionization energy increases across a period (higher Z_eff) and decreases down a group (higher n).
Example Calculation
Estimate IE of sodium: Z_eff ≈ 2.2, n = 3.
- 01IE = 13.6 × Z_eff² / n²
- 02IE = 13.6 × (2.2)² / (3)²
- 03IE = 13.6 × 4.84 / 9
- 04IE = 13.6 × 0.538
- 05IE = 7.31 eV ≈ 706 kJ/mol
- 06Actual Na IE = 5.14 eV (estimate is rough)
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