Question

The luster of a metal is due to

• A. its high density
• B. its high polishing
• C. its chemical inertness
• D. presence of free electrons

Answer 1

The correct option is D

presence of free electrons

(D)

• In order to look shiny or lustrous, the substance must reflect the light falling on it.
• Metals are the ones which are electropositive in nature and have the tendency to lose electrons and form cations. Due to these mobile electrons, the light falling on the metals get reflected back and gives a sheen appearance.
• Examples of metals: Copper (Cu), Aluminum (Al)

(A)

Since density can not be related to the shiny appearance of any substance, this option is incorrect.

(B)

Since polishing is done to increase the sheen appearance of metal, polishing can not be the reason behind the shiny appearance of metal.

(C)

Since metals are chemically active but not inert, this option is incorrect.

Final Answer: Hence, option (D) is correct. The luster of a metal is due to the presence of free electrons.