Elemental by Tim James

Author:Tim James [James, Tim]
Language: eng
Format: epub
ISBN: 9781468317022
Publisher: The Overlook Press
Published: 2019-04-15T04:00:00+00:00

WHY DO METALS CONDUCT AT ALL?

As you read from left to right across the periodic table you’re gradually increasing the number of protons in the nucleus. The more proton charge you have, the more electrons will be pulled inward and the smaller your atom becomes, meaning we see a decrease in atom size along each row.

Atoms on the left are therefore big and diffuse with great, floppy orbitals. Their electrons are also a long way from the nucleus with nothing much keeping them in place. This makes them ideal for sharing electrons with other atoms since the electrons have very little incentive to stay put.

When you get these bulky atoms together, their orbitals start mixing not just on a one-to-one basis but over the entire population. The atoms are so happy to share that when you solve the Schrödinger equation to describe millions of metal atoms, the result is a kind of mega-orbital—a turbulent free-for-all, which physicists call “the electron sea.” This network of overlapping orbitals means electrons can easily slosh from one side of the structure to the other.

Touch any piece of metal and beneath your fingertips you’ve got a swarm of electrons flitting back and forth at will. These movements are random but if we can persuade the electrons to travel in one direction at the same time we have an electric current.

In smaller molecules, formed by elements on the right, gaps between the orbitals make it hard for electrons to move, so they won’t conduct. That doesn’t mean, of course, that it’s impossible to force an electron through an insulator. Teflon, the most insulating material on Earth, can still be made to conduct but you need a fierce amount of energy to persuade the electrons to hop across the orbital gaps.

A substance with a conductance over 1 million siemens per meter is classified as a conductor while a substance below 0.01 is an insulator. Admittedly there’s a huge gap between 0.01 and 1 million siemens per meter, but very few substances fall in this region. Those that do are deemed “semi-conductors.”

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