Calculator
Enter totals in kJ/mol for one mole of ionic compound. Use negative values for exothermic terms when your selected convention requires them.
Example data table
| Compound | Metal atomization | Nonmetal atomization | Ionization total | Electron affinity total | Lattice formation | Formation enthalpy |
|---|---|---|---|---|---|---|
| NaCl | 108.7 | 121.0 | 495.8 | -349.0 | -787.0 | -410.5 |
| MgO | 150.0 | 249.0 | 2,189.0 | -141.0 | -3,795.0 | -1,348.0 |
| CaF2 | 178.0 | 159.0 | 1,735.0 | -656.0 | -2,635.0 | -1,219.0 |
These rows are illustrative practice values for checking workflow and sign handling.
Formula used
Core cycle:
ΔHf = ΔHat(metal) + ΔHat(nonmetal) + IEΣ + EAΣ + Ulatt,form + correction
Meaning of terms:
- ΔHf = enthalpy of formation of the ionic solid.
- ΔHat(metal) = total atomization or sublimation of the metal.
- ΔHat(nonmetal) = total atomization of the nonmetal.
- IEΣ = sum of ionization energies needed for the cation.
- EAΣ = sum of electron affinities for the anion formation.
- Ulatt,form = lattice formation enthalpy from gaseous ions.
- Correction = optional extra energetic term when your convention needs it.
When bond mode is enabled, nonmetal atomization is calculated as: (nonmetal atoms in formula unit ÷ atoms per elemental molecule) × bond dissociation energy.
How to use this calculator
- Enter the compound label so your result and exports are easy to read.
- Choose the quantity you want to solve for from the solve menu.
- Select your lattice sign convention before entering lattice data.
- Add all known cycle terms in kJ/mol for one mole of product.
- Enable bond mode if you want automatic nonmetal atomization from elemental bond data.
- Press the calculate button to show the solved value above the form.
- Review the summary table, component table, and Plotly graph for sign consistency.
- Use the CSV or PDF buttons to export your current result set.
FAQs
1. What does the Born Haber cycle calculate?
It links formation enthalpy to atomization, ionization, electron affinity, and lattice terms. This lets you estimate one unknown energy from the remaining known steps.
2. Why can lattice enthalpy be negative or positive?
Different textbooks use different conventions. Formation convention treats lattice creation as exothermic and usually negative. Dissociation convention treats lattice breakup as endothermic and usually positive.
3. Should electron affinity always be negative?
Not always. The first electron affinity is often negative for halogens, but later electron additions can be positive. Enter the total value that matches your chosen cycle definition.
4. What is bond mode for?
Bond mode converts bond dissociation data into nonmetal atomization automatically. It is useful for diatomic elements like chlorine, fluorine, oxygen, and similar elemental molecules.
5. What units should I enter?
Use kJ/mol for every energy field. All terms should correspond to one mole of the ionic compound formed, not one mole of atoms or ions alone.
6. Can I solve for formation enthalpy directly?
Yes. Select formation enthalpy as the target, then provide the remaining cycle terms. The calculator sums the energetic pathway and returns the predicted ΔHf.
7. What is the additional correction field for?
It gives flexibility when your data source includes an extra energetic adjustment or when you want to reconcile a custom convention without editing the standard fields.
8. How do I check whether my signs are correct?
Compare the summary table with the contribution graph. Endothermic steps should raise the total, while exothermic steps should lower it under the formation convention.