free electron

2013-04-17 8:24 pm

University physics note reads:

1) Electrical conductors are materials in which some of the electrons are free electrons. Free electrons are not bound to the atoms.

2) Electrical insulators are materials in which all of the electrons are bound to atoms.

But I am not quite understand that why free electrons are not bounded to the atoms in metal. According to my understanding in the word 'bounded to xxx', it means something is free from the influence of something, and in this case free electrons are free from the attraction of the atoms and have enough energy to escape from its surface.

回答 (1)

天同

2013-04-18 12:03 am

✔ 最佳答案

Atoms in metals are held together by "metallic bond", which is a lattice of +ve metal ions in a sea of delocalized electrons. Such delocalized electrons are free to move and thus got the name "free electrons".

This property lies on the fact that most metal atoms have one or two electrons in the outermost orbit (the valency electrons). Due to the shielding effect of inner orbit electrons, these outermost electrons experience small attractive force from the +ve charged mucleus. Thus they can easily be detached from the orbit and become "free" electrons.

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