Bromine is not a gas inside a working light bulb. In fact, bromine is a liquid at room temperature and would be very dangerous to have inside a light bulb.

Instead, the gas inside a working light bulb is argon or nitrogen. These gases are inert (non-reactive) and help prevent the filament from oxidizing (burning) too quickly.

Here's why:

* Oxygen is very reactive and would quickly cause the filament to burn out.

* Argon and Nitrogen are inert gases that don't react with the hot filament, allowing it to last longer.

Let me know if you have any other questions!