Why Are Some Materials Better Conductors/Insulators than Others?

[mindboggling]

why are some materials better conductors/insulators than others?

it'll helped if explained at the atomic level

thanks

 

[cristo]

Is this a homework question? If so.. post some of your thoughts on the matter.

 

[mindboggling]

no, it's not a homework question. Just asking because i feel curious

after thinking about it for abit, i guess that the rate of conduction is related to the density of the object. So... a solid is a better conductor than a gas because the atoms in a solid are closer together. However is this true for metal ( a good conductor) and rubber ( a bad conductor)? Are my thoughts right?

 

[cristo]

You are right on your thoughts about a solid being a better conductor than a gas. Metals are better conductors that nonmetals, since they have free electrons which can move thoughout the substance. A metal structure is made up of positive ions fixed into place, with a "sea" of free electrons. If one end of a metal rod gets heated, then the ions at that end vibrate faster, and so an electron colliding with it gains kinetic energy, then moves to the colder end, and collides with an ion there, passing on the kinetic energy.

In non-metals, there are no free electrons, and the only way in which heat is passed down the material is by the ions vibrating, and pssing these vibrations onto their nearest neighbour.

 

[mindboggling]

ah so it really depends on the atomic structure of the material. If so, how does metallic, covalent and ionic compounds compare. Is one generally more conductive than the other, or it really depends?

Thankas cristo