Question

Why does only lithium react with nitrogen while other alkali metals do not

Answer 1

Lithium is the smallest atom among alkali metals. ... When Lithium reacts with nitrogen gas at room temperature (N2), it forms Lithium Nitride (Li3N) which is stable, because the lattice energy released from the formation of Li3N is high enough to make the overall reaction exothermic.

Answer 2

Lithium is the only group 1 element that can form a stable alkali metal nitride (at standard conditions), the other group 1 elements (such as sodium, potassium, rubidium,...) will react (at different reaction conditions) to form their respective nitrides (in the case of rubidium, Rb3N (rubidium nitride)), but the compound will be unstable and decompose quickly. The reactions of the alkali metals (other than lithium) with nitrogen would not release enough lattice energy and would thus be endothermic, so they do not form nitrides at standard conditions