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Which gas is commonly used in electric bulbs to prevent the oxidation of the tungsten filament?
Nitrogen
Argon
Helium
Carbon Dioxide
Argon
Argon, a noble gas, is used in electric bulbs to provide an inert atmosphere that prevents the high-temperature tungsten filament from oxidizing. Because argon is chemically unreactive, it does not combine with the hot tungsten filament, thereby significantly increasing its lifespan.
Argon, a noble gas, is used in electric bulbs to provide an inert atmosphere that prevents the high-temperature tungsten filament from oxidizing. Because argon is chemically unreactive, it does not combine with the hot tungsten filament, thereby significantly increasing its lifespan.
Think of Argon as a 'protective bodyguard' that surrounds the tungsten filament, standing between it and the 'aggressive' oxygen molecules that would otherwise destroy it.
ARgon = ARrest Oxidation
W+O2тАЛтЖТWO3тАЛ тАФ The oxidation reaction that destroys the filament
TmeltingтАЛтЙИ3695┬аK тАФ The melting point of tungsten
Tungsten has a very high melting point of approximately 3695┬аK, allowing it to glow brightly when heated. However, at these temperatures, it reacts readily with oxygen to form tungsten oxide (WO3тАЛ), which would cause the filament to burn out instantly. By filling the bulb with an inert gas like argon (often mixed with nitrogen), the oxidation reaction is inhibited, and the gas molecules also help suppress the evaporation of tungsten atoms from the solid filament surface.
Tungsten is used for filaments due to its high resistivity and high melting point.
Noble gases are chemically inert due to their stable valence shell configuration (ns2np6).
Filling the bulb with inert gas slows down the sublimation of the tungsten filament, maintaining its structural integrity longer.
Prevents rapid burnout of the filament
Increases the operational lifespan of the bulb
Non-toxic and non-flammable
Argon conducts heat away from the filament more than a vacuum, slightly reducing efficiency compared to a perfect vacuum, though this is outweighed by the lifespan benefit.
Incandescent light bulbs
Fluorescent lamps (often mixed with mercury vapor)
Nitrogen is sometimes added to Argon to create a higher pressure environment inside the bulb, which further suppresses filament evaporation.
Option A (Nitrogen) is inert but less effective than Argon at suppressing evaporation. Option C (Helium) is too thermally conductive, cooling the filament. Option D (Carbon Dioxide) would react with the tungsten at high temperatures.
B is correct тАФ Argon is a noble gas that provides an inert environment, preventing the oxidation and premature degradation of the tungsten filament.
Always remember that 'Noble' gases are group 18 elements characterized by their full valence electron shells, making them chemically non-reactive in most standard conditions.
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