Current?

[taymor]

flow of electrons is called current which i know. my question here is that is that are those electrons moving from on the atoms shell to another atoms shell?

[ajb]

It is more subtle than that for metals or semiconductors. You have the notion of the conduction band, which is a range of electron states with energies sufficient enough to free an electron from binding with its atom, so that it can move freely within the atomic lattice of the material. Electrons in these states are delocalised and not really attached to any specific atom.

 

It is these electrons that are responsible for the conduction of electricity as well as heat.

 

You should also look up the notion of valance electrons and the band gap.

 

 

 

[Enthalpy]

In a molecule, atoms (usually pairs) share some electrons to make bonds.

In a metal, all atoms share some electrons at the scale of the whole wire. This is what makes it metallic.

These electrons already shared can move easily.

(Ajb, apologies for paraphrasing...)

[evansste]

My understanding is "yes", the electrons that are in the outer orbits of one atom, move to the outer orbit of a neighboring atom. However, the reason electricity moves so fast is because it's a domino effect. If you have a wire, one electron that starts on one end, doesn't physically travel to the other end near the speed of light. Instead, it simply jumps to the orbit of the neighboring atom, which causes an electron from that atom to jump to the next atom, and so on. It's this rapid "cause and affect" phenomenon that makes electrons appear to be moving near the speed of light. As electrons jump from one orbit to another, they do manage to migrate across the length of the wire, but not near the speed of light. At least, that's how I've always understood it.

[Enthalpy]

No.

 

Conduction electrons are delocalized to the complete piece of metal. They don't belong to one atom. That's a metallic bond.

[evansste]

@Enthalpy, it seems as if you're talking about valence electrons -- electrons that can easily move from the orbit of one atom to the orbit of another atom. I think that the difference between our responses is a matter of perspective when describing electrical models. I speak in terms of atoms because an elemental electrical conductor, such as copper or aluminum, could theoretically be cut into smaller and smaller pieces until you have individual atoms. Each of these atoms would have their own valence electrons. When these atoms are put together to make a larger conducting material, the electrons are allowed to move throughout the material, which is what I called a "domino effect" as they move from orbit to orbit. You say that the valence electrons "don't belong to one atom", while I say that they "move from atom to atom". From my perspective, this is just two different ways of saying the same thing . Others may agree or disagree.

[ajb]

In materials the interactions of all the orbitals specific to each atom in isolation form the band structures we see. It is the differences in these bands, and in particular the band gap, that control the nature of the electric conduction: metals, semiconductor and insulators.

Remember, the conduction band is a range of electron states with energies sufficient enough to free an electron from binding with its atom, so that it can move freely within the atomic lattice of the material.

The valence band is the highest range of electron energies in which electrons are present at absolute zero. Electrons in these bands are bound to the atoms.

For insulators, the conduction band is higher than that of the valence band, so it takes a lot of energy to delocalise their valence electrons. There is a gap between the valence and conduction bands. Insulators do not conduct electricity well at all.


Metals have many free electrons in the conduction band. The conduction band overlaps with the valence band and their is no band gap.


The middle road is found in semiconductors, which have a small band gap. It does not take much energy to delocalise the electrons and therefore conduct electricity.

The graphic below may help illustrate this.



http://en.wikipedia.org/wiki/Conduction_band

[Enthalpy]

@Enthalpy, it seems as if you're talking about valence electrons[...] I speak in terms of atoms because a conductor could be cut into individual atoms [...] When these atoms are put together to make a larger conducting material, the electrons are allowed to move throughout the material, which is what I called a "domino effect" as they move from orbit to orbit. You say that the valence electrons "don't belong to one atom", while I say that they "move from atom to atom". From my perspective, this is just two different ways of saying the same thing.

- There are no valence and conduction electrons in a metal, as no separated bands exist.

- If separating the atoms, this is not a metal any more. A metal is a lot of atoms, adn is defined by the metallic bond, which is delocalized.

- "Jump between the atoms" is not the same as "shared among all atoms". The electrons are shared among all atoms of a metal, and need no minimum energy added by the external field to move. Nor are electrons local to one atom. Each and every state is global to the whole metal, over many 1000km in a power grid for instance.