Apparent Metallic Paradox

I do not know with any level of certainty but I will hazard a guess.

First, something I do believe you do understand from your use of the electron sea analogy but I feel this should be stated. The electrons that "move" when current flows are not ionizing the atoms. When one of these atoms donates an electron to their neighbor in a conductive flow, another electron fills the void for that atom. [I know that this is a classical analogy for an actual quantum mechanic effect but I no longer can claim even rudimentary proficiency in QM math.]

So conductivity is not only a question of how easily an electron can move out of an atom but also how easily one can move in at the same time.

An additional factor that I believe comes into play should be considered with what phenomena resistivity measures, self heating during a net current flow. For heating to happen the average kinetic energy must be raised by the nucleus vibrating more in its matrix of the solid. These metals that are more chemically reactive must impart more energy of the current flow into wiggling the whole atom along with the process of giving and receiving the valence electrons.

Thank you for being the first to respond. I was getting concerned that no one was going to even comment.

.

I considered the 'one for one swap' model initially and found it lacking. Things like the hall effect, capacitance of adjacent co-normal plates, and the significant variations in charge that can occur from geometry alone (such as charge moving to the outside of a sphere but not being on the inside); offer fairly conclusive evidence that the sea of electrons really is sloshing around and the atoms haven't instituted anything similar to an exorbitant core trade in 'refund' for electrons.

.

Your comment on the vibrations generated by current flow seem on the right track, but I'm not reaching the connection, yet. Just to throw an extra wrench in there, although the trend I mentioned is apparently the predominant one, it isn't without exception. Aluminum is highly reactive and a great conductor....

There is always Wikipedia as a good place to start an understanding of the classical and quantum mechanical description of conductivity. What I was trying to describe is the Drude (aka classical) model. I like the animation at the Cambridge site. It implies the kinetic energy transfer (self heating) to the atom lattice I was also presenting. Keeping in mind that delectable quote you provided by George Box, "All models are wrong. Some are useful." There are inaccuracies in this classical model that the quantum mechanics model addresses.

Thank you.

Well since electricity flow is initiated with a magnetic field, one might think that the more magnetic the metal the better conductor it would be.....but there seems to be no relationship at all....what's up with that?

That's good thinking. I'll look at the various types of magnetic interactions para, ferri, ferro, etc, and the changes to those at temperature in comparison to resistivity at various temperatures and see if anything pops out.

Yes and along those lines is also the fact that the most magnetic metal(soft iron) makes the best electromagnet when wound with an energized conductor....but please, one step at a time....I look forward to your findings....

I think you will find the answer is in the post by Roger Pink,

http://cr4.globalspec.com/blogentry/24163/Gold-The-Noble-Metal-by-Roger-Pink

where he explains that Gold as a "loose/single" electron in the 6s sub-shell - meaning that sub-shell is not full. However from a chemistry point of view it is apparently easier to remove a 5d electron than a 6s electron because of screening effects (screening apparently relates to eccentricity of the orbit) - which leaves gold (surprisingly) as chemically inert.

My guess is that the "screening" effect does not come into play when single electrons are moving between atoms of the same type/size and so while chemically gold is inert, electrically it is not.

That is my take on it - any one got a better one.

So there is no relationship or correlation between the chemical stability and the molecular stability of these metals.....?

Actually, Roger's blog is what raised the question. I asked (twice actually) but I don't think many people saw it for some reason.

.

The loose single electron that is shaded is actually what seems like a paradox, not an explanation to me.

.

The explanation of each atom only exchanging electrons also falls short in my eyes. There are numerous properties of conductive metals that show us the sea of electrons moves with much less restriction than just one for one swapping. Consider what is necessary for two close flat metal surfaces to behave as a capacitor...and the very low voltage that can allow significant charge to build/deplete. The hall effect is another such example.

A hypothesis is posed that conductivity is related to the Sea of Electrons analogy. On examination of the observed data the evidence does not support this hypothesis. The simplest explanation is that the original hypothesis is wrong.

I think the answer is that the outer electrons have enough energy to jump from one atom to the next. This is much less than the amount of energy needed to escape the atom entirely (ionization).

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

Metals are said to lack band gaps because the valence and lattice conduction are not separate, and in many cases overlap.

.

I also don't think it is well supported that the electrons are mostly just jumping from one atom to the next, and being mostly filled in behind. One phenomena specific to metals demonstrates that the barrier to to an electron leaving is pretty low; galvanic corrosion. If gold and nickel are put in good electrical contact in hot sea water, there is going to be a ready flow of electrons to drive corrosion in nickel (and pretty much no corrosion on the gold) much faster than if the metals were not in contact. This suggests that it isn't the corrosion that necessarily is motivating the current flow, but perhaps the opposite.

You are right, it is not that simple. Gold is an excellent conductor but non-reactive for the reason that TrevorM (and Roger Pink) pointed out -- the inside of the outer shell is smaller than the outside of the shell below it (to paraphrase). The alkali metals (sodium, potassium ...) are very reactive but not particularly good conductors, so reactivity and conductivity don't necessarily correlate. Possibly the number of loose electrons donated by each atom and the inter-atomic distance are important.

For anyone interested in looking at any particular property for all of the elements, the following website is pretty good:

http://periodictable.com/Properties/A/IonizationEnergies.cl.html

What about the 'wave' theory that causes electron flow in my antenna? Does that in any way relate to electron flow in these metals?

I'm not sure. I need to look into it more closely. I was reading about the use of dielectric antennas a while back, I wonder if the same wave theory applies to dielectrics or if it is indeed specific to metals?

I am by no means an expert on this. I believe the "sea of electrons" usually refers to when a substance is cooled to near abosute zero, and becomes a superconductor. That is when the whole solid acts as a single molecule, and the electrons are "fluid". Elements that are good conductors of electricity are usually good conductors of heat. I don't think oxidation is related to either.

Thanks for the comment.

.

'Sea of electrons' describing a loosely coupled population of electrons in metals seems to be a fairly ubiquitous explanation for the conductivity and luster of metals. I haven't heard the term used to describe superconductivity. An explanation for high temperature superconductors often invokes cooper pair electrons, while an explanation of traditional superconductors usually involves phonon mediated electron pairing. I don't have a comfortable understanding of either, but these explanations do seem quite different from a sea of electrons.

.

I have to disagree with your opinion that oxidation is unrelated to conductivity. Conduction of charge is necessary (though not sufficient) by definition for oxidation. Considering things like the ability to control oxidation galvanically and the significant changes to electrical and thermal conductivity that result from oxidation of a substance, oxidation/reduction is pretty clearly dependent on conduction. The important differences are occur in scale and duration.

.

That relationship is what makes the lack of correlation between reactivity and conductivity in metals seem paradoxical. If oxidation/reduction is easy to segregate from conduction in your understanding then I guess no paradox would exit....I just haven't found an reliable path that way, yet.

"A sea of electrons" is a good way to look at it, with the molecules of water being comparable to electrons. Or better yet, "a swimming pool" of electrons wood be a good conductor, a "soda straw" of electrons would be a bad conductor, a "damp block of wood", or a "block of ice" would be a nonconductor.

There are two different concepts being introduced here. One is conduction, the other is reaction. Conduction is the ability to move a free electron from one place to another, reaction is the ability to either give up an electron (oxidation), or take in an electron (reduction). Conductivity is the tendency to provide conduction, reactivity is the tendency to provide reaction. These two abilities are not the same, not even closely related.

Other ideas which need to dealt with is "what is an electron"? and "what is a free electron"? An electron is a negative charge which exists as both a point and as a wave: this means the negative charge can be located, but the location is "smeared out", or fuzzy. A free electron is one which is not closely associated with a specific positively charged atomic nucleus; the ones that are associated with a nucleus are within what are called "orbitals", differently shaped spaces surrounding the center, or nucleus, with larger atoms having more "shells" in layers around them.

These ideas refer to atoms existing in a state separate from other atoms, either like themselves, or unlike themselves. When atoms are with other atoms they can "bond", or join together in groups called molecules, having less energy (and thus being more stable) when they are joined together then when they are apart. Examples of this for nonmetals are carbon dioxide, CO2, and methane, CH4. In these molecules the bonding electrons (those in unfilled shells) join together with other bonding electrons to fill their shells. In these two examples above, the carbon atoms, C, with four electrons in unfilled shells, can fill their shells (needing 2 or 8), by creating new shells, or "bonds", by joining with other atoms having different numbers of unfilled bonding electrons, so that bonds add up to filled shells. Oxygen has 6, so that by adding two oxygen atoms, two bonds can be formed of 8 each, with 6 from oxygen and 2 each from carbon. In methane, CH4, four bonds are created with two bonding electrons in each bond, one from hydrogen and one each from carbon. These new bonding orbitals have a new shape, no longer centered on one atom, but now being confined to surrounding two atoms. I selected as examples methane and carbon dioxide since they are gases and are stable molecules, without needing others nearby.

Metals are very different. Even though they can exist as single atoms, they prefer to be in a group. They have few bonding electrons, which can be reactive when they are in an exposed outer shell. The spectacular explosion when a piece of metallic sodium is thrown into water illustrates this. Note that the sodium is no longer in metallic form after it reacts with the water. Rust is another example of a metal reacting with water and changing its form. Metals (when in neutral metallic form) still have that issue of what about those unfilled shell electrons? The easy way out is to hybridize the orbitals (that is what happens when the bonds form in methane) into new shapes which extend around the nuclear centers donating the bonding electrons involved. Since these new orbitals extend throughout the metal, it is easy for an electron to enter at one location and exit at another, thus providing conduction. Conduction can also be accomplished by actually moving the charged atoms through space, or whatever material is present, but that is not metallic conduction.

Why conductive bonding electrons can be present in "noble" metals (nonreactive) relates to an issue referred to in an earlier post: as the atom gets bigger, the shells have more spaces and the energy levels get lower, so that the unfilled (bonding) shell electrons are no longer the most accessible for reaction, though the hybridized orbitals for conduction are larger and thus available for conduction.

Further analysis is available, but best at doctoral or postdoc level: mixing metals, gradations of concentrations in mixed metals, semimetallics, etc. Interesting stuff.

That is a good review of the standard explanation.

.

The standard explanation still fails to adequately predict or describe the behavior of metals in very basic electrical components such as the capacitor.

.

The standard explanation suggests that the high metallic conductivity and low reactivity of gold is the result of electron transfer only occurring easily as a 'one in, one out' transfer. The standard explanation suggests that metallic conduction, as a 'one in, one out' transfer, does not result in a variation in electron, or charge, density at various locations in the conductor.

.

That would mean gold parallel plates held very close together would not have much capacitance, because if conduction of electricity in a noble metal is substantially limited to being just 'one in, one out', no difference in charge can occur between the two plates, because they always have the same number of electrons to proton.

.

That is obviously not the case. The metal used for the plates affects capacitors mainly through conductivity/resistivity, but not nobility.

.

In this respect, the standard explanation, IMHO falls far short of being useful.