Which of the following is the best criterion of a metal?

Options

A. Lustrous surface
B. High density
C. High thermal conductivity
D. High three-dimensional electrical conductivity

Answer

D

Explanation

A lustrous surface is not a good criterion because several elements that are regarded as nonmetals, for example, silicon and iodine, have very shiny surfaces. Even a feq compounds such as the mineral pyrite, `FeS_(2)`(also called fool's gold) look metallic.
High density is not a good guide either because lithium has a density `1//2` that of water and osmiun has a density `40` times that of lithium. hardness is an equally poor guide, because the alkali metals are very soft. The ability of the elements to be flattened into sheets (malleability) or be pulled into wires (ductility) is sometimes cited as a common property of metals, but some of the transition metals are quite brittle. high thermal conductivity is common among the matals, but diamond, a nonmetals, has one of the highest thermal conductivities of any element.
High three-dimensional electrical conductivity is the best criterion of a metal because graphite (an allotrope of carbon) has high electrical conductivity in two dimensions.