pl. explain BAND THEORY

In a general way, a metal can be considered as a regular lattice of positive ions surrounded by an electron “ gas ” or “ sea ” that is mobile. This simple model accounts for many properties of metals. For example, the mobile electrons in metals enable them to be good electrical conductors. Because metal atoms can be displaced without destroying the lattice, metals can be shaped and retain their cohesiveness. Consequently, metals are malleable (can be hammered to change shapes) and ductile (can be drawn into wires). Moreover, the substitution of a different atom in the lattice is possible with the result being a solution of one metal in another, an alloy . The addition of other nonmetallic atoms such as carbon, nitrogen, or phosphorus increases the hardness of the metal while making it more brittle and less ductile.