# How is silver a better conductor than platinum?

Based on my understanding, platinum should be a better conductor than silver.

Here's my reasoning and assumptions. An atom's ability to conduct is based on the amount of energy required to displace electrons from it. The energy required is based (largely) on the number of electrons in the valence shell as well as the atomic radii (distance from valance shell to nucleus). There is a direct correlation between the magnetic attraction of the valence electrons to the protons and the radius of the atom. The further away the valence electrons, the lesser the energy required to displace the electron.

Let's take a look at silver:

You can see that silver has 5 electron shells, with 46 (18+18+8+2) electrons shielding the valence electron. It has one electron in the valence, so it is a good conductor.

Now, let's look at platinum:

Platinum, also, has a single valence electron. However, there are 6 electron shells -- one more than silver. There are 77 (17+32+18+8+2) electrons shielding the valence electron. Platinum has a larger radius than silver and, similarly, has a single valence electron.

I cannot find any explanations for the ranking of conductivity, but, in general, the interwebs provides an order of conductivity such as: silver, gold, copper, platinum. If platinum were, indeed, less conductive than gold and copper, why in the world would there be a market for platinum audio cabling -- assuming that platinum is more expensive?

Edit: Thank you for all of the replies, but none offer a concrete reason as to why silver is a better conductor. I am intrigued by the 'crystal structure' argument, but no one has provided the actual structures for platinum and/or silver and why the structure makes a difference. My search results show that platinum, silver, and gold all have the same structure -- 'face centered cubic'.

• A bit of a web search revealed several cables that were named "Platinum cables", but none that were actually made from platinum conductors. One major cable manufacturer actually has product lines named "coreplus", "silver", "gold", and "platinum", but only copper and silver are used as conductors, gold is plated onto some of the connectors, and platinum is not used at all. It's just that the "platinum" line is their highest-quality copper cable. Pretty obnoxious marketing, imho. – Todd Wilcox Oct 28 '17 at 19:52
• Fancy audio cables are complete bunk; don't bother using them as a source. – Someone Somewhere Oct 28 '17 at 22:19
• I tried searching for platinum audio cables, like @ToddWilcox described, and found the same result: a bunch of products with "platinum" in the name, but none of them claimed to be actually made of platinum. Most appeared to have been either silver or copper, some with gold-plating on the connectors. – Nat Oct 29 '17 at 1:33
• I'm definitely a layperson when it comes to Chemistry, but, doesn't Platinum also have a lot more protons? So, even though, in the simplistic model you described above, platinum's electrons are 'forced' into one more orbital, platinum has a lot more protons pulling on them. I know the electromagnetic field falls off rapidly with the square of the distance, but perhaps that extra distance of the one extra orbital isn't far enough to make it more conductive? – mkoistinen Oct 29 '17 at 1:52
• You need to know the crystal structure to get what are the defects that cause it to have resistivity ("losses", reciprocal of conductivity). Without that, you are not going to get far into conjecturing the electric characteristics of a material. Usually only using the periodic table of elements general properties won't be enough to determine all of the characteristics, even if it is pretty good for a rough first idea and estimate. – Vendetta Nov 6 '17 at 15:27

The situation is a lot more complicated than you described. When calculating the conductance of a metal, you first need to evaluate the allowed energy states of electrons in the bulk material, which is done by placing nuclei in a regular pattern (depending on the crystal structure). Usually, various approximations are used, which may or may not include the interaction between the electrons. Then you count the number of states at a given energy and get the so-called density of states. Then you start putting the electrons into these allowed energy states, until all electrons belonging to that element are added. And only then will you know if something is a conductor at all. For insulators, there is an energy gap between the highest occupied and the lowest unoccupied state, i.e. there are no states just above the energy of the highest filled state (the so-called Fermi energy). For metals, there is not.

I'm aware that this might be hard to follow if you are not familiar with these terms, but it's just to show that from a single atom sketch you can not conclude the electronic properties of the bulk material.

As to why there is a market for platinum cables - there is a market for anything people will buy, whether it makes sense or not.

• The gist is: in bulk material, energy levels are vastly different from a single atom, so you cannot use just the latter to make deductions on conductivity. – ivan_pozdeev Oct 29 '17 at 5:19
• Your last paragraph is absolutely right. Why in the world would there be a market for quantum bracelets, given that they have absolutely no effect? =) – user21820 Oct 29 '17 at 16:18
• platinum wires can be used in high temperature environment such as kilns where anything else would have melted long before – hyportnex Oct 31 '17 at 18:15

It appears that none of the responses so far have addressed the real reason silver is a better conductor than platinum.

The reason is electron scattering. The simplest model for conductivity in solid state physics is called the Drude model. This is a microscopic description of what happens to the electrons when you apply an electric field to get them moving. The Drude model explains Ohm's law of resistance, among other things, and it works surprisingly well for all simple conductors (and some not-so-simple ones).

The basic assumption of the Drude model is that electrons scatter off of things as they move around in the material. They basically scatter off the crystal lattice ions and can generate lattice vibrations (heat). Each material has a characteristic scattering time determined by the details of the crystalline structure, the temperature, and other things. In metals, electrons scatter around once every $10^{-14}$ seconds (!).

Ultimately, electrons in platinum scatter more rapidly than those in silver (by a factor of two or so). According to the Drude model, this means platinum has a lower conductivity.

As mentioned above, platinum does have a big practical advantage, though: it is a noble metal and does not oxidize (unlike silver). But gold is also noble and is a better conductor than platinum. The only reason I can think of why you might not prefer gold for audio cables is that it is soft. But the platinum cables are probably a gimmick.

• "Ultimately, electrons in platinum scatter more rapidly than those in silver (by a factor of two or so)." - Could you please elaborate why? – safesphere Oct 28 '17 at 4:09
• "[P]latinum cables are probably a gimmic" That applies to pretty much everything in the audio cable market, as far as I can see. – David Richerby Oct 28 '17 at 15:04
• Regarding your first sentence, your answer appears to be a more technical version of noah's. – Todd Wilcox Oct 28 '17 at 19:44
• A bit late, but: The electrons do not scatter off the crystal lattice unless there is an impurity or there are already thermal excitations. A pure crystal at zero temperature filled with non-interacting electrons is a perfect conductor. (Actually, in the quasi-particle picture the electrons scatter off the phonons, which are thermal excitations of the lattice and this is usually the dominant process at room temperature). – Sebastian Riese Jun 8 '18 at 22:07
• @SebastianRiese Truth. Bloch electrons are in eigenstates of the periodic lattice. Phonons make the lattice no longer perfectly periodic, so there’s scattering. – Gilbert Jun 9 '18 at 2:19

I'll add my two cents to the other answers from the audio perspective that hopefully would clarify the "platinum cable" issue.

First of all, there is a belief in the audio field that an ideal conductor, aside from being highly conductive, stable, and reasonably chemically inert, would also have one s-electron on the top orbit with all lower orbits full. There are only 3 metals to my knowledge fulfilling this criteria: copper, silver, and gold with all 3 positioned right one under the other in the periodic table.

Secondly, platinum plated connectors are extremely rare. I only know of a couple top brands in the world that use platinum for plating. Platinum is usually applied only on top of silver, whether silver is the base metal or the base metal is first plated with a silver underlayer.

There is a widespread misconception that silver oxidizes. This is incorrect. Solver does not oxidize at room temperatures. There also is an equally big misconception that silver oxide is a good conductor, thus tarnished silver connectors do not make a big difference. It is true that silver oxide is conductive, but the tarnish that easily develops on silver plated connectors is not silver oxide, because silver does not oxidize. Instead it is silver sulfide, brown to very dark brown (as opposed to pure black for silver oxide). Silver sulfide is not a conductor, but a semiconductor. Thus the idea that the silver tarnish does not affect the connection is a bad myth.

Silver aggressively reacts with hydrogen sulfide, a gas that naturally occurs in the natural gas and also comes from cooking eggs (even fresh) and from the car exhaust. If you have none of these three sources in your area (unlikely), then your silver plated connectors would stay shiny for much much longer. Platinum does not tarnish or oxidize at any temperature (e.g. platinum plated spark plugs), so it can protect silver from sulfur in the air.

It is a huge and wide spread misconception that the choice of metal for plating has anything to do with its conductivity. The typical plating thickness is between $0.3\mu m$ and $11\mu m$, give or take, plus has a substantial area of connection. Thus the contribution to the resistance of a thin cable several feet long is absolutely negligible.

The choice of metal for plating is based on the anti-tarnish properties, wear resistance, reasonable conductivity (usually at least 15% of copper), adhesion to the base metal, and marketing of noble metals.

Typical gold plating is done over a layer of nickel and thus essentially is just a nickel plating with a bit of extra protection from oxidation. Gold over copper is rarely used, because gold dissolves in copper. This makes a thin plating (less than $1\mu m$) pointless while a thick gold plating is expensive. Test results show that a gold plating of less than $3\mu m$ does not protect well from harsh environments. Gold also is not very durable for frequent connections, especially as a thin plating.

One of the most popular metals for high end plating today is rhodium. It can be applied directly over copper or silver, has a reasonable conductivity (like platinum), and does not wear (also like platinum).

• The gas which is added to natural gas to cause the odor is methyl mercaptan, not hydrogen sulfide. – Brian Rogers Oct 28 '17 at 5:56
• @BrianRogers You are right, thanks! I've updated the answer accordingly. The contribution of $H_2S$ from the natural gas is still quite substantial. Anything silver plated that I happen to put in the basement in the proximity of my gas appliances tarnishes very quickly and heavily. – safesphere Oct 28 '17 at 6:10
• Well then, I guess it's a good thing I never cooked eggs atop my engine block inside my music studio. – Mazura Oct 28 '17 at 20:48
• Re: It is a huge and wide spread misconception that the choice of metal for plating has anything to do with its conductivity. This does have a significant effect at high frequency due to the skin effect. Already at 1 MHz it is down to 80 µm for copper - at 100 HMz it is on the order of 1 µm. – Peter Mortensen Oct 30 '17 at 0:12
• @PeterMortensen I've trsted the skin effect in audio cables from 0.3mm to 1 inch in diameter and it has a dramatic effect on sound even in the 10kHz range. In wires, the skin effect is dominant (second only to the dielectric polarization). However, when the only plated parts are connectors, the plating actually is not all on the surface, but mostly between two connecting parts, plus their length is small compared to the cable length. In wires the cirrent runs along the plating = several feet, but in connectors only across = a few $\mu m$, so the plating resistance there is not as important. – safesphere Oct 30 '17 at 4:34

## protected by Qmechanic♦Oct 28 '17 at 6:55

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