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I am writing an article for kids, which is on conductors and insulators of electricity.

If I make a statement that "All metals are electrical conductors and all non-metals are electrical insulators" Am I right?

Are there any metals which are bad conductor of electricity?

Are there any non-metals which are good conductor of electricity?

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Well, I can't say that all non-metals are insulators, as non-metals include semiconductors. – orion Feb 28 '12 at 5:56

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Non metals

Most certainly. Carbon in graphite form is a good conductor. Metalloids are usually goodish conductors as well (they're actually semiconductors).

Metals

Mercury and Gallium are not as good conductors as most metals (but they are good conductors). Their conductivities are two orders of magnitudes less than most metals.

Note that mercury/gallium still are better conductors than graphite.

See this table if you want.

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well, metals are those elements which have similar properties because of lots of valent electrons loosely attached to the nucleus....By definition, they have lots of free electron. Hence, they are good conductors.. – Vineet Menon Feb 28 '12 at 5:36
@VineetMenon Yes, but Hg and Ga aren't that good. I've mentioned that they're still good conductors, just not as good. – Manishearth♦ Feb 28 '12 at 6:19
@dmckee Thanks; fixed. – Manishearth♦ Feb 28 '12 at 6:19
@Manishearth: ya, but without exception all metals are good conductors. High conductivity is what defines, among other things a material to be a metal. – Vineet Menon Feb 28 '12 at 7:16
@VineetMenon I never said the contrary: I've just mentiones that theyre not as good as most metals. I've said that they are good conductors. – Manishearth♦ Feb 28 '12 at 7:24
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Well, the metals are good conductors more or less by definition. However, really heavy metals like uranium or plutonium are not as good as usual.

The opposite is not true. There are lot of good non-metallic conductors. Semiconductors may be very good conductors, there are conducting polymers (not as good as copper or aluminum but properly produced they should conduct better than some metals), graphene is a good conductor. But probably the most funny example is superconducting cuprates which are ceramics.

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+1 for mentioning superconductors. That didn't strike me :p .IIRC metals are bad conductors at auperconducting temperatures. If that's true(not sure), you may want to add it to your answer. – Manishearth♦ Feb 28 '12 at 8:27
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Superconduction was discovered in mercury, i.e. a metal. So, some metals can become even better conductors. – MSalters Feb 28 '12 at 8:46
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@MSalters Aah. But I was referring to the fact that (i think) most metals become insulators at low temperatures. I think iron and copper do that. – Manishearth♦ Feb 28 '12 at 10:10
@Manishearth: Indeed. So, for the target group (kids), you're better off skipping the details. If you tell them about superconductors, tell them that they're entirely different from normal conductor materials. – MSalters Feb 28 '12 at 13:04
@MSalters Yup! Though kids usually want to know more about the exotic stuff and don't care about the rest =P. Usually a little note that 'at extremely low temperatures, many metals stop conducting and certain nonmetals become "superconducting"--an interesting role reversal'. Stuff like this keeps their interest in the topic--which is most probably the underlying goal. – Manishearth♦ Feb 28 '12 at 13:11

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