What this calculator does
Lattice energy (Kapustinskii equation) works out ionic crystal lattice energy from ion charges, radii and formula-unit count. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
The inputs explained
| Field | What to enter |
|---|---|
| Cation charge magnitude | A number. Starts at 1. |
| Anion charge magnitude | A number. Starts at 1. |
| Cation radius (pm) | A number, measured in pm. Starts at 102. |
| Anion radius (pm) | A number, measured in pm. Starts at 181. |
| Ions per formula unit | A number. Starts at 2. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with cation charge magnitude
Every other input is held at the calculator’s starting values while cation charge magnitude varies. Select any row to load that scenario into the calculator.