Science, Tech, Math › Science Electrical Conductivity of Metals Share Flipboard Email Print The Balance / Colleen Tighe Science Chemistry Chemistry In Everyday Life Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate by Terence Bell Terence Bell wrote about commodities investing for The Balance, and has over 10 years experience in the rare earth and minor metal industries. Updated January 11, 2020 Electrical conductivity in metals is a result of the movement of electrically charged particles. The atoms of metal elements are characterized by the presence of valence electrons, which are electrons in the outer shell of an atom that are free to move about. It is these "free electrons" that allow metals to conduct an electric current. Because valence electrons are free to move, they can travel through the lattice that forms the physical structure of a metal. Under an electric field, free electrons move through the metal much like billiard balls knocking against each other, passing an electric charge as they move. Transfer of Energy The transfer of energy is strongest when there is little resistance. On a billiard table, this occurs when a ball strikes against another single ball, passing most of its energy onto the next ball. If a single ball strikes multiple other balls, each of those will carry only a fraction of the energy. By the same token, the most effective conductors of electricity are metals that have a single valence electron that is free to move and causes a strong repelling reaction in other electrons. This is the case in the most conductive metals, such as silver, gold, and copper. Each has a single valence electron that moves with little resistance and causes a strong repelling reaction. Semiconductor metals (or metalloids) have a higher number of valence electrons (usually four or more). So, although they can conduct electricity, they are inefficient at the task. However, when heated or doped with other elements, semiconductors like silicon and germanium can become extremely efficient conductors of electricity. Metal Conductivity Conduction in metals must follow Ohm's Law, which states that the current is directly proportional to the electric field applied to the metal. The law, named after German physicist Georg Ohm, appeared in 1827 in a published paper laying out how current and voltage are measured via electrical circuits. The key variable in applying Ohm's Law is a metal's resistivity. Resistivity is the opposite of electrical conductivity, evaluating how strongly a metal opposes the flow of electric current. This is commonly measured across the opposite faces of a one-meter cube of material and described as an ohm meter (Ω⋅m). Resistivity is often represented by the Greek letter rho (ρ). Electrical conductivity, on the other hand, is commonly measured by siemens per meter (S⋅m−1) and represented by the Greek letter sigma (σ). One siemens is equal to the reciprocal of one ohm. Conductivity, Resistivity of Metals Material Resistivityp(Ω•m) at 20°C Conductivityσ(S/m) at 20°C Silver 1.59x10-8 6.30x107 Copper 1.68x10-8 5.98x107 Annealed Copper 1.72x10-8 5.80x107 Gold 2.44x10-8 4.52x107 Aluminum 2.82x10-8 3.5x107 Calcium 3.36x10-8 2.82x107 Beryllium 4.00x10-8 2.500x107 Rhodium 4.49x10-8 2.23x107 Magnesium 4.66x10-8 2.15x107 Molybdenum 5.225x10-8 1.914x107 Iridium 5.289x10-8 1.891x107 Tungsten 5.49x10-8 1.82x107 Zinc 5.945x10-8 1.682x107 Cobalt 6.25x10-8 1.60x107 Cadmium 6.84x10-8 1.467 Nickel (electrolytic) 6.84x10-8 1.46x107 Ruthenium 7.595x10-8 1.31x107 Lithium 8.54x10-8 1.17x107 Iron 9.58x10-8 1.04x107 Platinum 1.06x10-7 9.44x106 Palladium 1.08x10-7 9.28x106 Tin 1.15x10-7 8.7x106 Selenium 1.197x10-7 8.35x106 Tantalum 1.24x10-7 8.06x106 Niobium 1.31x10-7 7.66x106 Steel (Cast) 1.61x10-7 6.21x106 Chromium 1.96x10-7 5.10x106 Lead 2.05x10-7 4.87x106 Vanadium 2.61x10-7 3.83x106 Uranium 2.87x10-7 3.48x106 Antimony* 3.92x10-7 2.55x106 Zirconium 4.105x10-7 2.44x106 Titanium 5.56x10-7 1.798x106 Mercury 9.58x10-7 1.044x106 Germanium* 4.6x10-1 2.17 Silicon* 6.40x102 1.56x10-3 *Note: The resistivity of semiconductors (metalloids) is heavily dependent on the presence of impurities in the material. 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