Before learning to fix a motorcycle, I’d never given the conductivity of metals a second thought. Who would?
But as I started doing small tasks like replacing a carburetor or battery, it became clear just how much engineering genius is manifested in a 12V DC electrical system.
And how much of it I didn’t understand. That really bothered me.
One of those tasks was the materials used in electrical wiring. So I set out to learn everything I could about it.
And, while I found the answer, it also lead to many new questions about the world around us.
What is the most conductive metal?
The top 3 most conductive metals are:
The most conductive metal on earth is silver. While most people would assume copper is the most conductive metal because it’s everywhere, silver is slightly more conductive, with gold taking third place.
Guess there’s an argument to hand out silver medals first now at the Olympics? 🥁
But to understand why silver is more conductive than the other we need to go a level deeper.
What makes silver the most conductive metal?
Silver is the most conductive metal because it's valence electron on the outer shell moves more freely than in any other material when exposed to an electrical charge.
If we want to understand conductivity, we must first start with the atom.
To give a quick overview, atoms have a positive core, which consists of protons and neutrons, which are orbited by a field of electrons.
Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.
Let’s compare the copper, silver, and gold atoms:
The copper atom has 29 protons 35 neutrons and 29 electrons.
The silver atom has 47 protons 61 neutrons and 47 electrons.
And the gold atom has 79 protons 118 neutrons and 79 electrons.
All these atoms have one electron on the outer shell. We call this electron the valence electron.
What is a Valence Electron?
This valence electron is an electron found on the outermost shell of an atom. This atom has the ability to move from one field of an atom to another.
And if you are thinking- maybe the valence electron of silver moves “more easily” from one atom to another, than copper or gold, then you would be correct.
This is related to the property of resistivity, which is a measurement of how difficult it is to move the electrons through that material. Out of all the elements, silver has the lowest resistivity.
But what are the other factors that allow this silver valence electron to move more freely than the others? That comes down to a concept of orbitals.
What is an Orbital?
In simple terms, orbitals are the unique flight paths that electrons take around an atom.
We tend to fall into the trap of thinking that electrons orbit the nucleus of an Atom the way the Earth orbits the sun.
But that’s not the case. Check out this video to learn more.
Gold, copper, and silver all have unique orbitals. The orbital path the valence electron takes in silver allows it more move more freely than the valence of any of the other metals.
The Conductivity of Gold
Now if you are like me, you could get into the trap of thinking that gold could be more conductive. After all, there are more electrons in the field, ie “more shells”- so there must be a greater distance from the gold valence electron to the positive core right?
While there are more electrons, It is the distribution of electrons around the core that determines the resistivity.
And this also means that gold gives up electrons less easily than silver.
Why Do Electricians Use Copper Instead of Silver for Wiring?
If silver is the superior conductor, why don’t we use silver for everything?
The first answer is while it is superior in terms of resistance, it’s really not by much, copper is still a great conductor.
The second factor to consider is the cost. Silver and gold are rare earth metals. Copper is more abundant in nature and easier to mine
However, there are some cases, for example in some printed circuit boards, where the trade-off of price for lower resistance makes silver a better alternative to copper.
But what about gold, where do we use that? Gold can be useful because it is resistant to oxidization (ie corrosion). A common use case for gold is in specific connection points that are exposed to outside conditions.
It really blows my mind how smart the pioneers of physics and electricity must have been to work all of this stuff out.
Learning about the conductivity of metals opened up my mind to the fascinating world of atoms, electrons, and electrical charge. But it also raised a lot more questions (don’t get me started on the quantum stuff 🤯).
I hope you have learned a thing or two today. If you like it, why not give it a share.