Discussion

Electrical charge is able to move through substances when electrons or ionic charge is mobile and flows through the substance.  Metallic substances have delocalized electrons that are able to move freely through the materials allowing a current to flow.  Substances that conduct electricity freely are called conductors, while substances that impede the flow of electrons are called insulators.  Substances with covalent bonds generally have electrons that are localized in the bond and therefore are not free to flow.  

A detailed discussion is available on the Experiment 10 website.