Properties and Form/Structure
- Metals are shiny and lustrous when prepared or polished.
- Sheets of metal can be opaque or transmit green light, like gold leaf.
- Metals have the ability to lose their outer shell electrons easily.
- Metallic bonds hold metal atoms together, with delocalized electrons.
- The strength of metallic bonds varies among different elemental metals.
- Metals have a wide range of densities, from lithium being the least dense to osmium being the most dense.
- Magnesium, aluminum, and titanium are light metals of commercial importance.
- Metals are malleable and ductile, deforming under stress without cleaving.
- Metallic bonding contributes to the ductility of most metallic solids.
- Metals can undergo reversible elastic deformation described by Hooke's Law.
Electrical and Thermal Conductivity
- Metals have a range of energy states available to electrons at thermodynamic equilibrium.
- The Fermi-Dirac distribution describes the density of available states for electrons in metals.
- Metals are good conductors of electricity due to the mobility of electrons.
- The delocalized electrons in metals allow for efficient thermal conductivity.
- Metals have high electrical and thermal conductivity compared to nonmetals.
- Under high pressures, some elements and compounds that are not normally classified as metals can become metallic.
- Iodine gradually becomes a metal at a pressure of 40 to 170 thousand times atmospheric pressure.
- Sodium becomes a nonmetal at high pressures, but is expected to become a metal again at even higher pressures.
- Arsenic and antimony, commonly recognized as metalloids, exhibit non-metallic and balanced metallic properties, respectively.
- The boundaries between metals, nonmetals, and metalloids are not universally defined.
Applications and History
- Metals comprise 25% of the Earth's crust and have various uses in modern life.
- Metals are used in high-rise buildings, bridges, vehicles, home appliances, tools, pipes, and railroad tracks.
- Precious metals have been historically used as coinage, and coinage metals now include at least 23 chemical elements.
- The use of refined metals dates back to about 11,000 years ago with the use of copper.
- Bronze appeared in the fifth millennium BCE, followed by the production of early forms of steel and the discovery of sodium.
Alloys and Metal Types
- Alloys are substances composed of two or more elements, at least one of which is a metal.
- Alloys modify the properties of pure metals to make them less brittle, harder, resistant to corrosion, or have desirable color and luster.
- Iron alloys, including steel and stainless steel, make up the largest proportion of metallic alloys.
- Aluminum, titanium, copper, and magnesium alloys are also significant.
- Ferrous metals contain iron, including pure iron and alloys like steel.
- Non-ferrous metals lack significant amounts of iron.
Metal Data Sources