Re: what gas is contained in a light bulb?

hi Becky,

The gas in light bulbs is an inert gas, usually argon. It is required because the filament in a bulb (made from the metal tungsten) is heated to produce light. If oxygen were present, the filament would just burn away. If no gas were present, the filament would evaporate and the metal would condense all over the bulb.

See this page at How Stuff Works to learn all about how light bulbs work.