Question

why non-metals have a dull appearance?
A.They have many free electrons
B.They gain electrons easily
C.They do not have lustre
D.All of the above

Answer 1

Hint: Any substance has lustre or is bright, it is due to the reflection of photons by the mobile electrons on the metal surface. Non-metals do not have free electrons to lose, rather they gain the electrons, resulting in no reflection of the light.

Complete step by step answer:
-Non-metals are the elements in periodic table which form negative ions by accepting electrons from other electropositive elements. They have 4, 5, 6 or 7 electrons on their valence shell. They lack all the metallic properties and are good insulators of heat and electricity.
-They have high ionisation energies and high electronegativity as they gain electrons usually and form covalent bonds. They are mostly liquids and gases, only few are in solid state. They are non-lustrous because they don’t have shiny appearance.
-As they don’t have any free electrons available for excitation, when the light falls on them, it enters and gets absorbed without reflecting or transmitting any light. No reflection means no visible light or sparkle and thus, they do not have lustre and are dull in appearance. Lustre is a property of a substance to reflect the incoming light.

Hence, the correct option is (C).

Note:
It is stated that non-metals are not shiny or lustrous, but there are few exceptions. These are diamond and iodine. They are bright and shiny because of their shape, structure and electronic configuration respectively.