Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: thedoc on 08/03/2016 11:50:01
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Peter Culleton asked the Naked Scientists:
Hi, Chris,
I am an avid scuba diver. 'Trimix' contains helium instead of nitrogen, to reduce the chance of 'the bends' (possibly replacing some of the oxygen too, depending on the dive planned). It is (as you well know) an inert gas: it don't do nuthin'. So why (how?), perchance, is neon used for lighting? Why is radon "the second most frequent cause of lung cancer in France" (my translation of a French newspaper article)? Shouldn't inert gases hang loose and mind their own business?
Written reply not requested here. Especially if you were to discuss it on the radio....
Kind regards,
Peter Culleton
What do you think?
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Radon is (pedantically) not carcinogenic while it's still radon.
However, it falls apart by radioactive decay into what might be thought of as very fast moving shrapnel- that's what does the damage and causes cancer.
The neon in a neon light isn't doing chemistry so it's still fair to asy it is chemically inert. It's just that with a high voltage across it the electrons get strippedd off it and bashed round and the ionised neon, and the excited states of the atom are what's giving out light.
The effective temperature of the gas in a lamp like that might be 10,000 degrees or more so the idea of "chemistry" isn't quite the same as it is for more reasonable temperatures.
Finally, the "inert" gases are not quite inert.
https://en.wikipedia.org/wiki/Noble_gas_compound
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Bored Chemist beat me, but anyway...
Are inert gases really inert?
Noble gases are pretty inert (ie more insert than other columns in the periodic table), but not entirely inert.
Under extreme conditions they can form some compounds (often unstable compounds, easily reverting back to their noble isolation). See: http://en.wikipedia.org/wiki/Noble_gas_compound
So why is neon used for lighting?
The electronic structure of neon means that if you excite it with an electric current (rip its electrons off), it will glow with an orange color when the electrons return. Other noble gases emit other colors, allowing a wide range of bright advertising signs. They are named "neon lights" after the first application (neon), but they use a variety of noble gases.
The same mechanism also works with other gases, like sodium vapor and mercury vapor - but you don't need to heat up the noble gases to turn them into a vapor (and they aren't toxic like mercury).
Why is radon "the second most frequent cause of lung cancer in France"
Radon is radioactive. It is fairly common in granite areas.
It is not a chemical reaction with your lungs that causes cancer, but it is the fact that the radon nucleus breaks down after about 3 days into a different element (often Polonium). As radon decays, it emits a powerful alpha particle, which damages DNA, eventually leading to lung cancer (after years of exposure).
Even worse, while Radon is a gas, and easily breathed in, Polonium is a solid, which sits in your lungs, emitting even more damaging radiation.
See: http://en.wikipedia.org/wiki/Radon#Progenies