Which one has the highest lattice energy? The lattice energy of CaO(s) is –3460 kJ/mol the lattice energy of K2O is –2240 kJ/mol. then, lattice energy of CaO =2×2=4=4U since, charge on each ion in CaO is of magnitude 2.

Lattice energy of NaCl, U=1×1=1 since, charge on both ion is of magnitude 1. Lattice energy is directly proportional to the product of charge on ions in a crystal and is inversely proportional to the size of ions. Which has more lattice energy CaO or NaCl? 4.The ionic bond in CaO (-2, +2 ions) is stronger than that in NaCl (-1, +1 ions). Similarly lattice energy of any ionic compound can be calculated. So, the lattice energy of sodium chloride is -785 kJ/mol. The heat of formation for the whole reaction if it occurs in one step is -411 kJ/mol. The lattice energy released in this process should be negative and need to be calculated. The electron released for this process is the electron affinity and for this it is -349 kJ/mol.Ĭl (g) + e – → Cl – (g) ΔH EA1 = -349 kJ/mol Step 5:įifth and the last step is the formation of sodium chloride from it gaseous ions. The fourth step is the addition of electron to the chlorine atom to get negatively charged chloride ion in gaseous state. The ionisation energy for this step is +494 kJ/mol. Third step involved ionisation of sodium in gaseous state to get positively charged sodium ion by losing an electron. The energy of dissociation of bond energy is +122 kJ/mol.ġ/2Cl 2(g) → Cl (g) ΔH BE = +122 kJ/mol Step 3: Second step involved the dissociation of chlorine molecule to form chlorine atoms in gaseous state. The atomisation energy for this step is +107 kJ/mol. The energy change involved to get 1 mole of gaseous atom from its standard state is known as atomisation energy. This is known as atomisation and the energy change during this process is knows as atomisation energy. 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.

Lattice energy of nacl