By Drew Lichtenstein – Updated Mar 24, 2022

Lattice energy quantifies the strength of an ionic bond—the electrostatic attraction that holds ions together in a solid. Ett klassiskt exempel är bordssalt (NaCl). The Born–Landé equation allows chemists to calculate this energy from readily available crystal parameters.

Steg 1:Infoga de universella konstanterna

The Born–Landé expression contains several fixed constants that never change:

• Avogadros nummer, NA =6.022 141 79 (30) × 10²³ mol⁻¹
• Elementär laddning, e =1,602 176 487 (40) × 10⁻¹⁹ C
• Permittivity of free space, ε₀ =8.854 × 10⁻¹² C² J⁻¹ mol⁻¹

Step 2:Plug in the compound‑specific variables

For each salt, the following parameters differ:

• Madelung konstant, M (dimensionless; varies with crystal structure)
• Katjonladdning, Z⁺
• Anjonladdning, Z⁻
• Nearest‑neighbour distance, r₀ (i meter)
• Född exponent, n (typiskt intervall 5–12)

Step 3:Evaluate the Born–Landé equation

Gitterenergin (E) beräknas som:

E = -\frac{N_A M Z^+ Z^-}{4\pi \epsilon_0 r_0}\,[1-\frac{1}{n}]

Compute the expression inside the brackets first, then multiply by the prefactor. Det resulterande värdet uttrycks i kilojoule per mol (kJ mol⁻¹) och kommer alltid att vara negativt, vilket återspeglar den exoterma karaktären av gitterbildning.

Viktig anmärkning

Do not drop the leading negative sign—omitting it will give a positive value, which is physically incorrect.

For deeper insight, consult the original Born–Landé derivation or recent crystallography texts.