What colorless, odorless gas glows orange-red when electricity is discharged through it?

A neon light is not really much more than a fluorescent tube (actually, it’s less as it needs no phosphor coating on the inside), neon tubes contain the noble gas neon, surprise, surprise. Pass an electric discharge through a tube containing low pressure neon and it will glow with that familiar orange-red glow, so evocative of late-night bars and sleazy movies.

A neon light uses a very high voltage to propel an electric current through a low-density gas of neon atoms held in a glass tube. Charges from the electrode at each end of the tube fly through the gas colliding frequently with neon atoms and transferring some of their energy to the neon atoms. This kicks the neon atoms into a higher energy, excited state, with an electron in a higher orbital than normal. This excited state does not last and as the electron loses energy the atom drops back to a lower energy state and releases a photon of light. The energy of this photon is equivalent to the energy fall and for neon atoms that coincides with an energy that produces a reddish glow.

More Info: www.sciencebase.com

Test your knowledge

What are your thoughts on this subject?

34 Comments

fishrmn

Back in the early 70's worked with a man who made neon signs. Was interesting work.

Armadillo

Keith Beedles, some light switches glow orange or red-orange.

Chris Braun

Lynne Zeman, a noble gas means that the atom's outermost (valence) electron shell is already completely full of electrons (8).Thus, there is no exchanging or sharing of electrons with other atoms to become more stable (it's as stable as can be), making it nonreactive.

Corey Taylor

Trixie Pettman-South, Nope, only red. For those other colors, you'll have to add Argon.

teacherchicky

I answered radon but it recorded neon.

Eileen Dunn

Neon sounded to do with coloured light.

Lynne Zeman

Jeanmarie Daugherty, thanks, I found your research interesting. I too, checked Google to find what defined a "noble" gas. Low reactivity - sometimes referred to as "inert". But I assumed different colors of the tube used made the varying colors. Did not know it was to the addition of other gases. Thanks again.

Jeanmarie Daugherty

I questioned the gas that made the orange-red color, and guessed wrong. I then looked up what gases produce which colors in "neon" lights and found the following on Wikipedia: "The color of the light depends on the gas in the tube. Neon lights were named for neon, a noble gas which gives off a popular orange light, but other gases and chemicals are used to produce other colors, such as hydrogen (red), helium (yellow), carbon dioxide (white), and mercury (blue)"