In a reaction between a halogen and a metal, if the valency of the metal is greater will there be more halogen atoms present in the ionic compound/metal halide salt produced?

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?