Input parameters
Example lattice enthalpy data
This table shows typical values for several ionic compounds. Use it to compare your calculated values with literature-scale trends.
| Compound | z+ | z- | M | n | r (pm) | Approximate lattice enthalpy (kJ·mol-1) |
|---|---|---|---|---|---|---|
| NaCl | +1 | -1 | 1.7476 | 9 | 282 | -780 |
| MgO | +2 | -2 | 1.7480 | 8 | 212 | -3790 |
| CaO | +2 | -2 | 1.7476 | 8 | 240 | -3410 |
Formula used in this calculator
This tool applies the Born–Landé equation for lattice enthalpy:
U = - NA M z+ z- e² (1 - 1/n) / (4 π ε0 r)
The expression combines electrostatic attraction, represented by the product of ionic charges and Madelung constant, with short‑range repulsion captured by the Born exponent term.
How to use this calculator
Begin by selecting an ionic compound and identifying the charges of the cation and anion. Enter these as z+ and z- in the input fields.
Next, input the appropriate Madelung constant and Born exponent. Supply the interionic distance with the correct unit. Press the calculate button to obtain lattice enthalpy in kJ·mol-1 and optionally export results as CSV or PDF.
Lattice enthalpy in ionic chemistry
Lattice enthalpy quantifies the energy released when gaseous ions combine to form an ionic solid. High magnitude values indicate strong electrostatic interactions and usually correspond to high melting points and hardness in crystalline materials.
Because it reflects ion charge, distance, and crystal geometry, lattice enthalpy is central to understanding trends across groups and periods for many ionic compounds.
Born–Landé parameters in practical calculations
The Madelung constant summarizes how each ion interacts with all others in the crystal lattice. It depends exclusively on structure type and remains constant for a given geometry.
The Born exponent describes short‑range repulsive forces between overlapping electron clouds. Choosing realistic values ensures your computed energies remain consistent with experimental estimates and theoretical models.
Charge, distance, and stability relationships
Increasing ionic charge, while keeping all other parameters constant, makes lattice enthalpy more exothermic and stabilizes the solid. Similarly, shorter interionic distances increase attraction, enhancing lattice strength.
Comparing families such as alkali halides or alkaline earth oxides highlights direct relationships between ionic size, charge density, lattice enthalpy, and thermal stability.
Connections with solution and acid–base chemistry
Dissolving an ionic solid requires breaking lattice interactions while forming hydration interactions with solvent molecules. The balance between lattice enthalpy and hydration enthalpy governs solubility trends for salts.
To study these effects in aqueous systems, you can pair this tool with a molarity calculator or an ionic strength calculator when preparing electrolyte solutions.
Teaching and self‑study applications
In the classroom, lattice enthalpy examples help students visualize how microscopic charge interactions influence macroscopic properties like hardness, melting point, and solubility.
Learners can adjust parameters interactively, reinforce conceptual understanding, and cross‑check textbook exercises by comparing their manual calculations with values generated by the calculator.
Frequently asked questions
What is lattice enthalpy?
Lattice enthalpy is the enthalpy change when one mole of an ionic solid forms from its constituent gaseous ions. It measures the overall strength of electrostatic interactions in the crystal.
Why does the calculator use the Born–Landé equation?
The Born–Landé equation combines long‑range Coulombic attraction with short‑range repulsion. It gives a useful theoretical estimate of lattice enthalpy using measurable structural parameters for many ionic solids.
Which units should I use for interionic distance?
You can enter distances in picometres, nanometres, ångströms, or metres. The calculator internally converts your chosen unit into metres before applying the Born–Landé expression to compute lattice enthalpy.
How accurate are the calculated lattice enthalpies?
Accuracy depends on the quality of parameters you supply. Using realistic Madelung constants, Born exponents, and interionic distances generally yields values comparable to textbook or experimentally derived lattice enthalpies.
Can this tool compare different crystal structures?
Yes. By changing the Madelung constant and relevant distances, you can compare how rocksalt, cesium chloride, zinc blende, or wurtzite structures influence lattice enthalpy for similar ionic pairs.
How do I export my results as CSV or PDF?
After running a calculation, scroll to the results table and click the CSV or PDF buttons. The browser will download your current input set and corresponding lattice enthalpy value.