When rubidium (Rb) reacts with iodine (I₂), it forms rubidium iodide (RbI). This is a typical ionic reaction where a metal (rubidium) reacts with a non-metal (iodine) to form an ionic compound.

Here's the balanced chemical equation:

2 Rb + I₂ → 2 RbI

The reaction is highly exothermic and produces a white crystalline solid, which is rubidium iodide.