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Liquid electrolytes ionize and hence a current can pass through them. So if a gas can ionize, can it conduct electricity too? If so, what are a few such gases?

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When gases get ionized, they're no longer gases, really, they're plasma. In fact, it's definition of plasma in physics that it's ionized gas. en.wikipedia.org/wiki/Plasma_(physics) Plasma is conductive, of course, and heavily responds to electromagnetism. –  Luboš Motl Sep 29 '12 at 11:30
The degree of ionization can be very different. It is not always 100%. Low pressure gases conduct currents at low voltage and are mostly gases than plasmas. –  Vladimir Kalitvianski Sep 29 '12 at 17:45
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Electric Conduction: At atmospheric pressure, air and other gases are poor conductors (Insulators) of electricity. 'Cause they don't have any free electrons to carry current. But, once free electrons are produced in gas by ionization (They become plasmas), discharge of electricity through gases appears. This could be done in many ways such as applying large potential difference across a gas column at very low pressure or by allowing high frequency EM-waves such as the X-Rays through the gas. This question is not proper to ask. Indeed, Gases become Plasmas once they're ionized..!

How? All Dielectrics have a certain value of breakdown potential - A potential which provides sufficient energy to break some covalent bonds and produce free electrons. These free electrons are accelerated by the applied electric field and they collide and ionize other atoms to produce more free electrons (Thus, they multiply by collision). This process is called Avalanche Breakdown. As there are large number of free electrons available for current flow

Examples: Discharge tubes, Lightning, etc.

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Gases do conduct electricity, as all materials do. However, they conduct electricity so poorly that we consider them insulators. "Electricity" requires the movement of electrons. In a gas, these electrons are too dispersed to provided any measurable current. The "lightning" example is slightly different. This refers to capacitative discharge. When the two sides of a capacitor (i.e. the ground and the clouds) store too much charge, that charge eventually jumps the dielectric (i.e. the stuff in between the ground and clouds). We still don't say that the dielectric "conducts" electricity, although it obviously does. The best insulators in the world could not stop a discharge of sufficient strength. The defining quality of a conductor is that it conducts electricity "more easily" than most substances. There is no perfect conductor or perfect insulator. In short, gases can conduct electricity, but they are considered insulators for the most part.

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