From an electrical conductivity standpoint, all elements currently known to Humans fall into one of the three main categories of: Insulators, Conductors, or Semiconductors. For clarification purposes, I am focusing on pure forms of these elements, as complex molecular structures tend to “break the rules” of these explanations, as their electrical properties come from the electron-bonds between elements, which is a little complex for anyone who isn’t a chemist. For example, wood is a decent insulator; however it is made of highly complex molecular structures composed of several elements. Likewise, stainless steel, a metal made from carbon and iron (elements that in pure forms can also conduct electricity), is actually a poor conductor compared to other metals. The image below shows the elements of the periodic table classified in the three forms of electrical conductivity.
Insulators – Materials that do not respond to the presence of an electric field as well as resisting the flow of charge are considered “insulators.” There are no “perfect insulators,” so for all materials, there is a certain electrical voltage at which the material will break down and allow current to force its way through. This is actually called the material’s “breakdown voltage.” The typical response to higher-voltage applications is to simply add more and more material between the conductor and any other material being protected. A good example of an insulating material in pure elemental form would be liquid nitrogen. For relative reference, insulators have an electrical resistivity on the order of 1016 Ohm-meters.
Conductors – Materials that naturally allow electric current to flow as well as those that respond to electric fields are called “conductors.” Most transition metals on the periodic table are natural conductors, with the addition of a few other elements, such as alkali metals. While noble-gasses are considered to be “non-reactive,” they are used in almost every application I can think of in some way, involved with electricity. In fact, the noble gasses are far more conductive than common gasses, such as oxygen or nitrogen, as the full-electron shell of the noble gasses allows them to more easily pass electrons to one another freely. For example, the neon gas in neon signs is just the gas with electricity being forced through it. The light that is being emitted is the gas heating up from the current being pumped through it, much like an old incandescent bulb. Conductors tend to have an electrical resistivity of about 10-8 Ohm-meters, meaning they allow electricity through with 1,000,000,000,000,000,000,000,000 (one-septillion) times the ease of an insulating material.
Semiconductors – Here’s where things get a little weird, as materials that are classified as “semi-conductive” are materials that can either allow or prevent current from flowing, depending on the energetic state of the material at the time. The most quintessential example of this property would be silicon, the first element to be widely employed in semiconductor technology. Pure silicon on its own has an electrical resistivity of around 102 Ohm-meters, however when impurities, or dopants, are added to the material, the relative resistivity drops to about 10-3, which means the same amount of electrical voltage applied to the material would suddenly result in 10,000 times the amount of current being released.
Thanks to the creation and addition of the periodic table on the web, it is now possible to see the electrical conductivity relationship of all of the known elements in their pure crystalline state. The image below depicts all of the elements and colors them based on their electrical conductivity. Elements that are more darkly colored conduct more electricity. With the elements shown as they are, it’s easy to see why societies everywhere have settled on using aluminum, copper, silver, and gold in almost all of our electrical and electronics applications. These elements simply allow more current to pass through them with the least resistance.