What is the mass number of an element

Using the periodic table, complete the table to describe each atom. type in your answers.a ? b? c? d? e? f?

Label a-f based on the table using c for concentrated and d for dilute

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?