Metals
. Metals, group of chemical elements that exhibit all or most of the following physical qualities: they are solid at ordinary temperatures; opaque, except in extremely thin films; good electrical and thermal conductors ; lustrous when polished; and have a crystalline structure when in the solid state. Metals and nonmetals are separated in the periodic table by a diagonal line of elements. Elements to the left of this diagonal are metals, and elements to the right are nonmetals. Elements that make up this diagonal— boron , silicon , germanium , arsenic , antimony , tellurium , polonium , and astatine —have both metallic and nonmetallic properties (see Periodic Law ). The common metallic elements include the following: aluminum , barium , beryllium , bismuth , cadmium , calcium , cerium , chromium , cobalt , copper , gold , iridium , iron , lead , lithium , magnesium , manganese , mercury , molybdenum , nickel , osmium , palladium , platinum , potassium , radium , rhodium , silver , sod