Carbon is the only nonmetal outside of the metalloid group that conducts electricity. Metalloids are a group of related nonmetal elements with some metal traits, including the ability to conduct electricity. Other nonmetals are electrical insulators.
The metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. Silicon and germanium are used commercially for their ability to conduct electricity. Arsenic and antimony are classified as semi-metals, or the most metallic members of the metalloid family. These two elements are the best conductors in the metalloid group.
Carbon conducts electricity and is classified as a semi-metal when in the form of graphite. Although it conducts electricity and heat like a metal or metalloid, graphite is not used commercially as a conductor. Instead, its softness makes it an effective lubricant for engines and industrial machinery. Graphite is one of two naturally-occurring forms of pure carbon; the other form is diamond, which does not conduct electricity.
Metals conduct electricity due to their atomic structure. Electrons move freely between grouped atoms of the same metal element, allowing an electrical charge to move through the metal. Because electrons are tightly bound to their parent atoms in nonmetals, an electrical charge cannot pass from one nonmetal atom to another. This gives most nonmetals their electrical insulation.