Fluorine has greater electron affinity than mercury or tungsten and hence fluorine could have been in electric bulbs.Because it can attract electrons easily than the metals which mostly repel extra electrons, so fluorine should release more energy[light].Then why wasn't it used?

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    $\begingroup$ Fluorine is way more dangerous than mercury $\endgroup$ – Lighthart Jul 15 '16 at 15:58
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    $\begingroup$ And etches glass, which isn't good for the bulb. But, it seems to me that the question is driven more on misunderstandings of how the different types of light bulbs work. The connecting of the electron affinity and supposing F would release more light is just wrong. $\endgroup$ – Jon Custer Jul 15 '16 at 16:03
  • $\begingroup$ and it is not just a $very$ $very$ dangerous gas it reacts with most everything including, I expect, a hot tungsten filament. Mercury is used mainly in high pressure arc lamps, or low pressure discharge lamps and not in domestic filament bulbs. The gas in a domestic light bulb is mainly there to stop the filament oxidising and is usually a rare gas or nitrogen. The bulb may also be evacuated. $\endgroup$ – porphyrin Jul 15 '16 at 16:28

First, you mix two types of lamps: incandescent lamps use conducting material with highest possible melting point. It was graphite at first, tungsten later. Mercury lamps use vapors. Obviously F2 cant be used in the first type. What about the second type? Any material inside of a lamp needs to cycle between to states to emit light. High electron affinity by itself is not necessarily good. Materials that are transparent and can contain F2 are at best expensive or might not yet exist. Glass and plastic will react with fluorine.

People generally need a light of a certain color. They use neon, argon and krypton to get different colors. Mercury works better because it has much more energy levels available, so it doesn't emit a single color, but a spectrum that is close to sum light. The bulb itself is coated to re-emit lite and make it even more "sun like".

As for the light intensity - you can increase it by using more powerful supply of electricity. People do try to increase the yield of light, but it has little to do with electronegativity.

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    $\begingroup$ "Mercury works better because it has much more energy levels available, so it doesn't emit a single color" - not true it emits UV radiation and that's why luminophore coating is necessary. Be careful with quality of your posts. It's more important than quick answering and answering to low quality questions is often a waste of time. $\endgroup$ – Mithoron Jul 15 '16 at 18:38
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    $\begingroup$ @Mithoron - not exactly - there are clear mercury lamps in use, mainly for outdoor lighting. As wiki says, it has a blue-green tint, so is not used indoors where it makes humans look bad. Now, the phosphors do convert the various UV lines to visible (that the glass would absorb), and help greatly with the color balance. $\endgroup$ – Jon Custer Jul 15 '16 at 18:54
  • $\begingroup$ @JonCuster Oh, ideed, should have checked. $\endgroup$ – Mithoron Jul 15 '16 at 19:08

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