Why is it that all the least reactive metals are the best electrical conductors?

[gribbon]

Just a thought: why is it that all the least reactive metals are the best electrical conductors?

 

For example, Silver, Gold and Platinum are the top three conductors, whereas other good conductors are also highly unreactive (Best electrical conductors: silver, copper, gold, aluminum, calcium, (these two are exceptions) beryllium, tungsten. If an element gives up it's electrons readily, (making it highly reactive) then shouldn't that mean it will be a great electrical conductor? Why isn't Cesium the best conductor?

[eric l]

A good question ! But the simple fact that you can give yourself two exeptions to the "rule" is an indication that it is not actually a rule at all. Maybe the fact that silver, gold and platinum are not liable to oxydation at the surface makes them better conductors - the contact-resistance where they touch the measuring equipment will be lower than if they had corroded surfaces. Aluminium does show oxydation at the surface, but this layer of aluminiumoxide itself protects the metal against deep corrosion.

I had a more or less similar thought once, as I passed through a glass passage while speaking on the cell phone. The signal was uite OK when passing through the clear glass section, but an other section had the glass coated with a reflective coating, and there the signal was much weaker. Of course, light is an electromagnetic signal, same as the radiowaves for the cell phone. I suppose the reflective coating was a very thin layer of metal, and "concluded" that metals, being good conductors for electricity are actually bad conductors for electromagnetic waves.

I never tested the theory any further, but you might do so on your theory about reactivity and conductivity, e.g. starting by comparing data for conductivity and electropositivity.

[Jay-qu]

This is a good question - more generally I would like to pose: What makes a metal a better conductor than any other metal?

 

I tried to do a search but turned up nothing.. so this is what I got.

 

Notice that Gold silver and copper are in the same group on the periodic table, with platium in the one next to them. Elements in the same group have the same valence electron configuration and since it is the valence electrons that take part in the flow of electricity, there must be a connection.

[Tormod]

From wiki:

For the purpose of elecronics and electrical engineering, materials are classified according to their electrical resistance, which describes how readily they allow electric current to pass when a voltage is applied. Apart from conductors, materials are classed as insulators (very poor conductors), semi-conductors (basically, materials whose ability to conduct electricity can be controlled), and superconductors which (below a critical e, usually a very low one) offer no significant electrical resistance, allowing circular currents, once established, to flow indefinitely.

[eric l]

After my post on yesterday, I looked up some data in an old Dutch "polytechnisch zakboekje" (polytechnical pocketbook). This used to give me all kind of data on all kind of stuff. And it has a table with specific resistances !

Cross referencing with wikipedia, I found the same data (I used the Dutch version)

metal symbol

silver / Ag / 0,0167 / 0,0036 / -0,8 / 1,93 / 1,6

copper / Cu / 0,0175 / 0,004 / -0,34 / 1,95 / 1,7

gold / Au / 0,021 / 0,0035 / -1,68 / 2,45 / 2,35

aluminium / Al / 0,038 / 0,0039 / 1,67 / 1,61 / 2,7

tungsten / W / 0,056 / 0,004 / - / 2,36 / 5,4

platinum / Pt / 0,111 / 0,0024 / -1,2 / 2,28 / 10,6

mercury / Hg / 0,95 / 0,0009 / - / 2,00 / 95,8

hydrogen / H / - / - / 0 / 2,20 / -

 

The number after the symbol gives the specific resistance in µOhm.mm²/m

the next number is the temperature coëff (increase in resistance/°C)

The third number is the electronegativity. All these data from my "polytechnical pocketbook".

Fourth and fifth numbers are from wikipedia, and give electronegativity (Pauling scale) and and specific resistance in µOhm.cm (hence 1000* the value in column 3).

First conclusion : gold and certainly platinum are not that good as conductors. (If platinum is used for electrical contact points, it is because of its resitance to corrosion even at high temperatures.) Even copper is better than gold ! (I included tungsten because it is widely used in lightbulbs, and mercury because it is used in some switches).

Second conclusion : no correlation between resistivity and electronegativity.

Third conclusion : I should try and find a better way to include an Excel table in my post.

(Fourth conclusion : where is that spell checker when I most need it ?)

[DFINITLYDISTRUBD]

glass coated with a reflective coating, and there the signal was much weaker. Of course, light is an electromagnetic signal, same as the radiowaves for the cell phone. I suppose the reflective coating was a very thin layer of metal, and "concluded" that metals, being good conductors for electricity are actually bad conductors for electromagnetic waves.

Perhaps the EMF waves are absorbed converted to heat and not passed on through the air which is an insulator. Transformers, reciever chips, and generators basically convert EMF into electricity while transmitting circuits convert the other way (though the function of transformers is... most simply put to generate EMF pulses in the primary and convert these pulses into electricity in the secondary coils).

 

Tungsten is primarily used in electrical components because of it's extreme ability to withstand high temps and in some instances because of its resistance to abrasion.

 

Mercury is (though not as much there days it seems) used because it reliably provides an almost friction free switching circuit and in some cases because it is able to be converted to a conductive vapor at relatively low temperatures (Ie. as in MV and fluorescent lights).