Which type of materials generally have a lustrous appearance can be shaped to form sheets or wires, and are good conductors of heat?

• A. Metals
• B. Nonmetals
• C. Ceramics
• D. Metalloids

Answer: (A)

Metals have a set of linked properties that make this answer correct. They exhibit a lustrous surface because of the way their electrons reflect light, giving a shiny appearance. The atoms in metals are bonded in a way that creates a sea of delocalized electrons, which move freely and efficiently transfer energy, so metals are excellent conductors of heat. This same electron mobility also lets metals be shaped repeatedly without breaking: they are malleable enough to form sheets and ductile enough to be drawn into wires. Nonmetals and ceramics generally lack this combination—nonmetals are typically poor conductors and not typically lustrous or malleable, while ceramics are usually hard and brittle and not good thermal conductors. Metalloids sit between metals and nonmetals and don’t consistently exhibit all three traits. So metals best meet all three criteria: lustrous appearance, ability to form sheets or wires, and good heat conductivity.