Labeled Diagram of Born-Haber Cycle

All 10 parts on the diagram

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The six arrows 6

Atomization of sodium Solid sodium becomes separate gaseous atoms. Also called the sublimation of sodium; it takes energy in.
First ionization energy Each gaseous sodium atom loses one electron. It takes energy in.
Atomization of chlorine Chlorine molecules are broken into separate atoms. Half a mole of molecules gives one mole of atoms.
Electron affinity Each chlorine atom gains one electron. It is the first step that gives energy out.
Lattice energy The gaseous ions come together as the solid. It cannot be measured directly, so the cycle is used to find it.
Enthalpy of formation From the elements straight to the solid. It equals the sum of the other five steps.

Levels and the axis 4

Elements in standard states Solid sodium and chlorine gas, as they are found. The cycle starts from this level.
Gaseous ions Sodium ions and chloride ions, apart, as a gas. The lattice energy is measured from this level.
Solid sodium chloride The product: one mole of solid sodium chloride. It is the lowest level of the chart.
Energy axis Energy rises up the chart. An arrow that points up is a step that takes energy in.

How this list was compiled: Every step name and its direction checked on 2026-10-03 against Purdue University, General Chemistry Topic Review: Why Does Sodium Form NaCl? (https://chemed.chem.purdue.edu/genchem/topicreview/bp/ch7/whydoes.php); Wikipedia, text only: Born-Haber cycle and Lattice energy; chemguide: Lattice Enthalpy (https://www.chemguide.co.uk/physical/energetics/lattice.html); and Chemistry LibreTexts: Lattice Energy: The Born-Haber Cycle. Licence: own work

The drawing: Drawn for this site on 2026-10-03 from plain geometry, to scale from published enthalpy changes; nothing traced. Licence: own work

How it works

This labeled diagram of the Born-Haber cycle follows sodium chloride from its elements to the solid. Arrows that point up take energy in; arrows that point down give energy out. Study the names, then quiz yourself.

Read the full guide

Reading the cycle

Start at the elements in their standard states: solid sodium and chlorine gas. Three steps climb. Sodium becomes gaseous atoms, each atom loses an electron, and chlorine molecules are broken into atoms. Two steps fall. Each chlorine atom gains an electron, then the gaseous ions come together as the solid.

What the cycle is for

Lattice energy cannot be measured directly. By Hess's law the five steps add up to the enthalpy of formation, so the lattice energy is worked out from the other values.

One mole of sodium chloride needs only half a mole of chlorine gas, which is why three levels read ½Cl₂.

Questions and answers

What is a Born-Haber cycle?

An energy diagram that splits the making of an ionic solid from its elements into steps: atomization, ionization, electron affinity and lattice energy. It applies Hess's law and is used mainly to work out a lattice energy.

What are the steps of the Born-Haber cycle for NaCl?

Atomization of sodium, the first ionization energy of sodium, atomization of chlorine, the electron affinity of chlorine and the lattice energy. Together they add up to sodium chloride's enthalpy of formation.

Which steps of a Born-Haber cycle are exothermic?

For sodium chloride, the electron affinity of chlorine and the lattice energy give energy out, and so does the enthalpy of formation. Atomization and ionization take energy in.

How do you label each step in a Born-Haber cycle?

Read the formulas on the two levels an arrow joins. Solid to gaseous atoms is atomization, an atom losing an electron is ionization energy, an atom gaining one is electron affinity, and gaseous ions to solid is lattice energy.