# What is the lattice energy?

When $N a C l$ dissolves in water, the crystals disappear on the macroscopic scale. On the atomic scale, the $N {a}^{+}$ and $C {l}^{-}$ ions in the crystal are released into solution. The lattice energy of a salt therefore gives a rough indication of the solubility of the salt in water because it reflects the energy needed to separate the positive and negative ions in a salt.
Opposite of this picture is this example: The lattice energy of $N a C l$ is the energy given off when $N {a}^{+}$ and $C {l}^{-}$ ions in the gas phase come together to form the lattice of alternating $N {a}^{+}$ and $C {l}^{-}$ ions in the $N a C l$ crystal.