How does lattice energy relate to the periodic table?

Lattice energy relates to the periodic table through the trends in ionisation energy, electron affinity and atomic radii.

Lattice energy is the energy required to break apart an ionic compound into its individual ions. It is a measure of the strength of the forces between the ions in an ionic solid; the greater the lattice energy, the stronger the forces. The lattice energy of a compound can be affected by the charge on the ions and the size of the ions. These factors are directly related to the trends in ionisation energy, electron affinity and atomic radii on the periodic table.

Ionisation energy is the energy required to remove an electron from an atom. It increases across a period from left to right and decreases down a group. This is because as you move across a period, the number of protons in the nucleus increases, pulling the electrons in closer and making them harder to remove. As you move down a group, the outer electrons are further from the nucleus and easier to remove. Therefore, elements with high ionisation energies tend to form positive ions and have high lattice energies. For a more detailed explanation, see Trends in Ionisation Energy.

Electron affinity is the energy change when an electron is added to an atom. It generally increases across a period from left to right and decreases down a group. This is because as you move across a period, the atomic radius decreases, so the added electron is closer to the nucleus and more strongly attracted. As you move down a group, the added electron is further from the nucleus and less strongly attracted. Therefore, elements with high electron affinities tend to form negative ions and have high lattice energies. To learn more about this concept, visit Electron Affinity in Periodic Trends.

Atomic radii decrease across a period from left to right and increase down a group. Smaller ions have higher lattice energies because the ions are closer together and the forces of attraction are stronger. Therefore, elements with small atomic radii tend to have high lattice energies. For further details on this topic, refer to Atomic Radius.

In summary, the lattice energy of a compound is directly related to the trends in ionisation energy, electron affinity and atomic radii on the periodic table. Understanding these trends can help predict the lattice energy of a compound.