The luster or shiny appearance of a metal surface is mainly due to the presence of free mobile electrons in the metallic structure. Is this statement correct or incorrect?

Introduction / Context:
This question explores why metals have a characteristic shiny appearance known as metallic luster. In solid state chemistry and materials science, metallic bonding and free electrons play a crucial role in both electrical conductivity and optical properties. Understanding the reason for metallic luster helps connect abstract ideas about electron behavior with visible properties of everyday materials like copper, aluminium, and silver.

Given Data / Assumptions:

• The statement claims that metal luster is due to free electrons.
• We need to decide if this statement is correct or incorrect.
• We assume a basic model of metallic bonding with a sea of delocalized electrons.

Concept / Approach:
In the metallic bond model, metal atoms release some of their valence electrons, which become delocalized and move freely through the crystal. These free electrons are able to absorb, reemit, and reflect light over a wide range of wavelengths. This interaction with light gives metals their shiny, reflective surfaces. The same free electrons also explain why metals are good conductors of electricity and heat. Therefore, the presence of free electrons is the key reason behind metallic luster.

Step-by-Step Solution:

Verification / Alternative check:
Textbook discussions of metallic bonding usually mention three connected properties: luster, electrical conductivity, and thermal conductivity. All three are traced back to the same feature, namely the presence of delocalized electrons in the metallic lattice. Experiments show that metals with more free electrons generally have better conductivity and strong reflectivity. This supports the idea that free electrons are responsible for metallic luster and confirms that the statement is correct.

Why Other Options Are Wrong:

• Option B: Tightly bound electrons in directional covalent bonds are more typical of non metals and do not produce the same shiny metallic reflection.
• Option C: Metals are conductors, not insulators; this option contradicts fundamental electrical behavior.
• Option D: Density can influence appearance but it is not the direct cause of luster; free electrons are the primary reason.
• Option E: The statement has a definite truth value; it is clearly correct based on metallic bonding theory.

Common Pitfalls:
Many learners mix up the roles of bound and free electrons. They sometimes think that any type of electron cloud can cause shine. However, metallic luster is strongly linked to the ability of electrons to move freely, which allows them to respond quickly to incoming light waves. Another mistake is to think that metallic luster and conductivity come from different causes, when in fact they share the same origin in the delocalized electron sea model. Keeping this connection in mind simplifies the understanding of metallic properties.

Final Answer:
The statement is correct because free mobile electrons in metals reflect incident light and produce metallic luster.