Metals are a fundamental class of chemical element, constituting the majority of elements on the periodic table, generally located on the left and center blocks. They are defined by a distinct set of physical and chemical behaviors. Metals are foundational to modern industry, used extensively in construction, electronics, and manufacturing.
Defining Physical Properties
Metals possess a highly reflective appearance known as metallic luster, caused by the interaction of light with the material’s surface. This is due to the presence of freely moving, delocalized electrons that absorb and re-emit photons. This electron “sea” is also responsible for the metal’s ability to be physically reshaped without fracturing.
Malleability describes a metal’s capacity to be permanently deformed, hammered, or pressed into thin sheets without breaking. Ductility is the ability of a metal to be drawn out into a thin wire under tensile stress. Both properties arise from the non-directional nature of the metallic bond.
In the crystal lattice, positive metal ions are held together by the surrounding mobile electron cloud. When a force is applied, layers of metal atoms can slide past one another. The delocalized electrons shift to maintain the cohesive bond, preventing the structure from shattering. This flexibility distinguishes metals from brittle materials.
Energy Transfer and Phase Characteristics
Metals are highly efficient at transferring energy, both as heat and electricity. The delocalized electron sea serves as a rapid transport system for thermal energy. When heated, free electrons quickly absorb kinetic energy and transfer it throughout the material via collisions.
Electrical conductivity is also excellent in metals because the delocalized electrons are not bound to any single atom and move freely in response to an applied electrical potential. When a voltage is applied, these mobile charge carriers flow easily through the lattice, constituting an electric current. Silver and copper are known to be the best conductors, making them the standard materials for electrical wiring.
Most metals are solid under standard room conditions, with the notable exception of mercury, which is liquid. The strong electrostatic attraction between the positive metal ions and the surrounding electron sea means that metals generally have high melting and boiling points. Significant thermal energy is required to overcome these strong metallic bonds. Furthermore, metals typically exhibit high density because their atoms are closely packed within the crystal lattice.
Fundamental Chemical Behavior
A metal’s chemical identity is defined by its tendency to lose electrons during chemical reactions. Metallic elements typically possess one to three valence electrons, which they readily give up to achieve a more stable configuration. This loss of electrons results in the formation of positively charged ions, known as cations, a process called oxidation.
Because metals cause other species to gain electrons by supplying their own, they are classified as powerful reducing agents in redox reactions. The ease with which a metal loses its electrons determines its reactivity; for example, alkali metals in Group 1 are highly reactive due to their single, easily lost valence electron.
When metals react with oxygen, they generally form metal oxides, which display a characteristic chemical behavior. These metal oxides are typically basic in nature, meaning they will react with acids to form a salt and water. This tendency to form basic oxides, as opposed to the acidic oxides formed by non-metals, is a defining chemical property.