Calculator Inputs
Formula Used
Electron affinity is computed from the energy difference between a neutral atom and its corresponding anion.
If the anion has a lower energy than the neutral atom, the result is positive under this convention. That means adding an electron is energetically favorable.
1 eV = 96.4853321233 kJ/mol
1 eV = 96485.3321233 J/mol
1 eV = 23.060548867 kcal/mol
1 Hartree = 27.211386245988 eV
How to Use This Calculator
- Enter a label or element name for your calculation.
- Type the neutral atom energy in a consistent unit.
- Type the anion energy in the same unit system.
- Select the input unit you used for both values.
- Choose the output unit for the final result.
- Set decimal places or scientific notation if needed.
- Click the calculate button to show the result above the form.
- Use the CSV or PDF button to save your report.
Example Data Table
These sample rows are illustrative input sets for practice and validation.
| Label | Neutral Energy (eV) | Anion Energy (eV) | Electron Affinity (eV) | Interpretation |
|---|---|---|---|---|
| Sample A | -13.60 | -14.35 | 0.75 | Favorable electron attachment |
| Sample B | -8.00 | -7.70 | -0.30 | Unfavorable electron attachment |
| Sample C | -20.00 | -21.50 | 1.50 | Strong positive affinity |
| Sample D | -5.20 | -5.20 | 0.00 | Threshold case |
Frequently Asked Questions
1. What does electron affinity measure?
Electron affinity measures the energy change when a neutral gaseous atom gains an electron. This calculator reports that change from neutral and anion energy inputs using one consistent sign convention.
2. Why can the result be positive or negative?
A positive result means the anion is lower in energy than the neutral atom. A negative result means the anion is higher in energy, so electron attachment is unfavorable for the supplied values.
3. Do both energy values need the same unit?
Yes. Neutral and anion energies must be entered in the same unit system before subtraction. The calculator then converts the final electron affinity into your chosen output unit automatically.
4. What sign convention does this calculator use?
It uses EA = E(neutral) − E(anion). Under this convention, positive values indicate favorable electron gain because the anion sits at a lower energy than the neutral atom.
5. Can I use Hartree or molar energy units?
Yes. The calculator accepts eV, kJ/mol, J/mol, kcal/mol, and Hartree. It converts everything internally to eV, then returns the result in your selected output unit.
6. Why does the graph compare neutral and anion energies?
The graph helps you see the energy gap that creates electron affinity. Larger vertical separation means a larger magnitude of affinity, while the direction of the gap explains the sign.
7. Is this tool suitable for classroom and lab review?
Yes. It works well for checking hand calculations, exploring sign conventions, and converting units quickly. For publication work, verify your source energies and reference method carefully.
8. What happens if neutral and anion energies are equal?
The result becomes zero. In that threshold case, the supplied data show no net energy advantage or penalty for adding an electron under the calculator’s chosen convention.