Which Gas is Filled in an Electric Bulb and Why is Tungsten Used in The Filament of Lamps?

Answer: Argon fills in electric bulbs. Argon is inert and does not give rise to any reaction that is chemical and further would not affect the tungsten filament. Argon’s main function is slowing down the evaporation process for tungsten filament. Argon is quite commonly used and is used to fill incandescent light bulbs. Argon increases the bulb life by preventing deterioration of tungsten filament at an alarming rate. 

Tungsten is used because it has:

• Tungsten has been reported to have a very low vapour pressure
• Tungsten has a melting point that is quite high