Lattice Energy
Estimate lattice enthalpy (U) using the Kapustinskii Equation
β What This Calculator Is & Why It Matters
The Lattice Energy Calculator uses the Born-LandΓ© equation (or the Born-Haber cycle) to estimate the immense amount of energy released when gaseous ions bind together to form a solid ionic crystal lattice.
Why does it matter? Lattice energy is the "glue" holding salts together. It dictates how hard a crystal is, how high its melting point is, and whether or not it will dissolve in water. A salt with an extremely high lattice energy (like AlβOβ) is physically indestructible and totally insoluble in water.
β The Formula Explained Simply
The Born-LandΓ© equation calculates this energy based on electrostatic attraction (charges) and repulsion (distance):
E = - (N_A Γ M Γ zβΊ Γ zβ» Γ eΒ²) / (4ΟΞ΅β Γ rβ) Γ (1 - 1/n)
Simply put: Higher charges (z) and smaller ion sizes (r) result in a massive increase in Lattice Energy.
β 3-5 Real-World Examples
Example 1: NaCl vs LiF (Size Effect)
Lithium and Fluorine are much smaller ions than Sodium and Chlorine. They can pack closer together (smaller 'r').
Result: LiF has a higher lattice energy than NaCl. LiF is harder and melts at a higher temperature.
Example 2: NaCl vs MgO (Charge Effect)
Na and Cl are +1/-1. Mg and O are +2/-2.
Result: MgO's lattice energy is roughly four times higher than NaCl's because (2Γ2) = 4. MgO melts at a staggering 2,852Β°C.
β FAQ Section (Google PAA Targeted)
What is the Madelung constant (M)?
It is a geometric factor that accounts for the specific 3D shape of the crystal lattice. A simple cubic structure (like CsCl) has a different Madelung constant than a face-centered cubic structure (like NaCl).
Why is Lattice Energy a negative number?
Forming a bond *releases* energy (exothermic). Therefore, the energy of the system drops, resulting in a negative value. However, textbooks often report it as a positive value, referring to the energy required to *break* the lattice apart. They are the exact same number, just opposite signs.
β Pro-Tips for Lattice Energy
- Charge Beats Size: When predicting which salt has a higher lattice energy, look at the charges first. A change from +1 to +2 has a much more massive impact on the math than the slight difference in atomic radius between elements.
β Related Calculators
β AI Explanation of Results
Our AI will compare your calculated lattice energy to the hydration energy of the ions (how badly water wants to pull them apart) and provide an educated prediction on whether the salt will actually dissolve in water.
About the Lattice Energy Calculator
Solve chemical kinetics and thermodynamics problems. Calculate Gibbs free energy, activation energy, entropy, or reaction rates.
This precision chemistry tool is designed for academic reference, laboratory workflows, and student education. It provides instant, real-time computational results with standard formulas and dimensional analysis inputs.