Metals are good conductors of electricity because of their atomic structure that allows electric charges to pass through freely. The atomic structure of metals is unique because of the presence of one, two or three valence electrons in the outer orbit of the atoms, and this is true for all metallic elements. These free-flowing valence electrons act as carriers of electricity, allowing the metal to conduct electrical charges throughout its structure with little resistance.
How Valence Electrons Conduct Electricity
All elements are made of atoms, which are neutral particles with a nucleus at the center and with negatively charged nucleus that are randomly orbiting around it. Metallic elements have one, two or three electrons that are orbiting around the nucleus called valence electrons.
Valence electrons are completely detached from the nucleus and moves freely. These electrons move randomly when there is no electrical field present. Once an electrical field is applied to the metal, the valence electrons line up from one end to the other end of the metal, relaying the electrical charge from one electron to the other.
Imagine a billiard table with the balls all in a line. The energy that was imparted to the cue ball will carry on to the next balls in line with efficiency. However, if the cue ball hits balls that are scattered about randomly, the energy that was imparted to it will quickly dissipate. More than fall in a straight line, valence electrons also have a strong repelling reaction, which means that they transfer the electric charge onto the next electron with little to no loss of energy.
Conductivity vs. Resistivity
The conduction in metals is measured via its conductivity and resistivity. The unit for measuring electrical conductivity is called Siemens. Resistivity is the exact opposite of conductivity, and it evaluates how strongly an element resists the flow of an electric charge.
When calculating for conductivity, the variable Siemens is represented by the Greek symbol sigma (σ), while the resistivity variable is represented by the Greek symbol rho (ρ). A higher Siemens score indicates good conductivity. In the same vein, lower resistivity score is likewise indicative of good conductivity.
Among all the metals, silver is the best conductor of electricity because it has the highest number of valence electrons. It ranks the highest in both conductivity and low resistivity. Because of the high cost of silver, however, its use in electrical equipment is limited, being used almost exclusively for sensitive equipment such as satellites and high-end circuit boards.
With electrical conductivity and low resistivity ranking next only to silver, copper is the most widely used conductor in a wide range of electrical equipment. Its lower production cost and abundance make copper the preferred metal when a large quantity of conductive material is needed for electrical applications.
Ranking third in conductivity and low resistivity, gold is also used for various electrical applications. Since gold does not corrode or tarnish, it helps extend the life of circuit boards and electrical connectors. Due to its high cost, however, gold is used sparingly in electrical equipment. It is used primarily as plating for circuitry and for small electrical connections.