Correct Option
The correct option is Metallic lustre.
Explanation
Metals exhibit distinct physical properties that differentiate them from non-metals. These properties include optical characteristics, mechanical strength, and acoustic behavior. The specific property related to the interaction of light with the metal surface determines its visual appearance.
Option Analysis
- Metallic lustre: Metallic lustre (Correct)
Metals, in their pure state, possess a shining surface known as metallic lustre. This phenomenon occurs because the free electrons present on the surface of the metal oscillate when light strikes them, reflecting the light and creating a shiny appearance. This is the direct cause of the shine observed after polishing. - Malleability: Malleability (Incorrect)
Malleability is the mechanical property that allows metals to be beaten into thin sheets without breaking. While gold and silver are highly malleable, this property relates to deformation under compressive stress, not visual shine. - Ductility: Ductility (Incorrect)
Ductility is the ability of metals to be drawn into thin wires. It is a measure of a material's ability to undergo significant plastic deformation before rupture, unrelated to its optical properties. - Sonority: Sonority (Incorrect)
Sonority refers to the property of metals to produce a ringing sound when struck by a hard object. This is an acoustic property, distinct from the visual characteristic of shine.
Key Takeaway
Metallic lustre is the specific optical property responsible for the shiny appearance of metals, whereas malleability and ductility refer to mechanical deformation capabilities.