23.1.1—Terms

Enthalpy of atomisation is the enthalpy change when one mole of gaseous atoms forms from an element in its standard state. Lattice energy here is the enthalpy change when gaseous ions form one mole of an ionic solid lattice.

State the direction and physical states before using a value in a cycle. Reversing a step changes its sign; lattice energy of dissociation is the opposite direction to lattice formation.

Na(s) → Na(g) contributes atomisation, while Na⁺(g) + Cl⁻(g) → NaCl(s) is lattice formation. Both are different from sublimation or hydration.

Do not call any solid-to-gas process atomisation, and do not mix lattice formation and separation conventions in one calculation.