371Metals Section
A metal (from Greek "μέταλλον" – métallon, "mine, quarry, metal") is an element,
compound, or alloy that is a good conductor of both electricity and heat. Metals are usually
malleable, ductile and shiny. The meaning of the term "metal" differs for various
communities. Many elements and compounds that are not normally classified as metals
become metallic under high pressures.
Structure and Bonding
hcp and fcc close-packing of spheresMetals typically consist of close-packed atoms, meaning that the atoms are arranged like
closely packed spheres. Two packing motifs are common, one being body-centered cubic
wherein each metal atom is surrounded by eight equivalent atoms. The other main motif
is face-centered cubic where the metal atoms are surrounded by six neighboring atoms.
Several metals adopt both structures, depending on the temperature.
In a metal, atoms readily lose electrons to form positive ions (cations). Those ions are
surrounded by de-localized electrons, which are responsible for the conductivity. The solid
thus produced is held together by electrostatic interactions between the ions and the
electron cloud, which are called metallic bonds.