---
title: "Lattice Enthalpy and Born-Haber Cycles"
description: "The energy released when gaseous ions come together as a lattice cannot be measured directly. It is found from a cycle built out of atomisation, ionisation, electron affinity and formation data."
canonical: https://lightmysky.com/learn/science/lattice-enthalpy-and-born-haber-cycles-mt_pUku4iUjYa
source: https://lightmysky.com/learn/science/lattice-enthalpy-and-born-haber-cycles-mt_pUku4iUjYa.md
retrieved: 2026-09-12
---

> **Agent view.** This is the Markdown twin of the page, for tools and assistants.
> When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md
> API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md
> Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt
> Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json
> Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`.

# Lattice Enthalpy and Born-Haber Cycles

The energy released when gaseous ions come together as a lattice cannot be measured directly. It is found from a cycle built out of atomisation, ionisation, electron affinity and formation data.

Subject: Science · Area: Chemistry · Ages 17 to 18
Page: https://lightmysky.com/learn/science/lattice-enthalpy-and-born-haber-cycles-mt_pUku4iUjYa

## Ready when they can

- Puts the steps of a Born-Haber cycle in order and gives the sign of each
- Calculates a lattice enthalpy from the other terms in the cycle
- Explains why lattice enthalpy gets more exothermic for smaller ions and for larger charges
- Compares a cycle value with one calculated from a perfect ionic model and says what a gap suggests about the bonding

## Lesson: Billing the Lattice

Lattice enthalpy is the energy released when one mole of solid forms from separate gaseous ions. The more exothermic the value, the stronger the lattice holds together. You cannot measure it directly, so you find it with a cycle.

A Born-Haber cycle splits formation into steps: atomisation of each element, ionisation of the metal, electron affinity of the non metal, then lattice formation. The steps must add to the overall formation enthalpy, which is Hess law applied to ionic compounds.

**Example.** Signs are predictable. Atomisation and ionisation take energy in, so they are positive. Electron affinity and lattice formation usually release energy, so they are negative. Know every step but one and you can calculate the missing value.

**Tip.** Small highly charged ions pull hardest, so magnesium oxide far exceeds sodium chloride. If the cycle value disagrees with a perfect ionic model, the gap points to covalent character with shared electron density.

**Recap.** Build the cycle, balance the signs, solve for the missing step, and read size and charge for the trend.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Ionisation Energy and the Evidence for Sub-Shells](https://lightmysky.com/learn/science/ionisation-energy-and-the-evidence-for-sub-shells-mt__suwzd1kVQ)
- [Hess's Law and Enthalpy Cycles](https://lightmysky.com/learn/science/hesss-law-and-enthalpy-cycles-mt_530V9czLOb)
- [Ionic Bonding: Electron Transfer and Charged Lattices](https://lightmysky.com/learn/science/ionic-bonding-electron-transfer-and-charged-lattices-mt_sf24C4YLtN)

## Opens up

- [Entropy and the Spread of Energy](https://lightmysky.com/learn/science/entropy-and-the-spread-of-energy-mt_a_2feH2gnE)
- [Close Packing, Unit Cells and Ionic Lattice Types](https://lightmysky.com/learn/science/close-packing-unit-cells-and-ionic-lattice-types-mt_LzpVzwrDm3)