MyMaths - Bringing Maths Alive. The Electromagnetic Spectrum Song - by Emerson & Wong Yann (Singapore) GCSE revision and A level revision. Year 9 Maths Practice. GCSE Science. Digital Dialects language learning games. Reactions of the Group 2 elements with air or oxygen. Energy is evolved when the ions come together to produce the crystal lattice. This energy is known as lattice energy or lattice enthalpy.
The size of the lattice energy depends on the attractions between the ions. The lattice energy is greatest if the ions are small and highly charged - the ions will be close together with very strong attractions. In the whole of Group 2, the attractions between the 2+ metal ions and the 3- nitride ions are big enough to produce very high lattice energies. When the crystal lattices form, so much energy is released that it more than compensates for the energy needed to produce the various ions in the first place.
The excess energy evolved makes the overall process exothermic. This is in contrast to what happens in Group 1 of the Periodic Table (lithium, sodium, potassium, rubidium and caesium). Lithium is the only metal in Group 1 to form a nitride. In all the other cases in Group 1, the overall reaction would be endothermic. Khan Academy.