Here the formation of sodium chloride is happening is few steps: Step 1:įirst step involved the formation of sodium atom in gaseous state from its standard solid sodium. Below is the Born haber cycle for the formation of sodium chloride crystal. The energy change will be same whether it reacts in few steps or in one step. For an example, the solid sodium and chlorine gas reacts to form sodium chloride crysltal. So the total energy involved to form a ionic compound from its elements will be same whether it happened in few steps or in one step. According to this law the energy change is same for a particular reaction regardless whether the reaction undergoes in one or several steps. The calculation of lattice energy can be done by using Hess’s law (for this case it is called Born Haber cycle).

Here we can see that the lattice energy of MgO is much greater than the lattice energy of NaCl. Thus +2 or -2 ions will release more lattice energy than the +1 or -1 ions. Lattice energy increases with increase of charge on the ions because of their more attractive force between them. Thus the attraction between them decreases and finally the less lattice energy released during the process. This is because with the increase of size of ions, the distance between their nuclei increases. As the size of halide increases down the group, the lattice energy decreases. Below is a graph of the lattice energy of lithium halide. a) Radius of ionsĪs the radius of ions increases, the lattice energy decrease. And lattice energy depends on two factors: size or radius of ions and charge of ions. The strength of ionic bond increases with the increase of lattice energy. That means, energy released when a cation and a anion combine together to form one mole of an ionic compound is know as lattice energy or lattice enthalpy. The energy released in this process is known as lattice energy or lattice enthalpy. After the formation of ions, they combine together to form ionic compound. Ionic compounds are more stable because of their elctrostatic force between the two opposite ions.

Equation of lattice energy of nacl