The electronic conductance depends on:

A. The nature and structure of the metal.

B. Composition of metallic conductor

C. The number of valence electrons per atom.

D. Temperature

E. Number of ions.

Choose the correct answer from the options given below:

A, B, C and D only

The correct answer is option 2. A, B and D only.

Let us explore each factor to understand how it influences electronic conductance:

A. The Nature and Structure of the Metal

Nature of the Metal: The inherent properties of a metal, such as its atomic structure and bonding, play a crucial role in its conductance. Metals with a high density of free electrons tend to be better conductors. For instance:

Silver has the highest electrical conductivity of all metals due to its high free electron density and atomic structure. Copper is also a great conductor because of its atomic structure that allows electrons to move freely.

Structure: The crystal structure of a metal affects how easily electrons can move through it. For example, metals with a face-centered cubic (FCC) structure often have higher conductivity compared to those with other structures.

B. Composition of Metallic Conductor

Impurities and Alloys: The presence of impurities or alloying elements can impact the conductance of a metal:

Impurities: Introducing foreign atoms into a metal can disrupt the regular arrangement of atoms, increasing electron scattering and reducing conductivity.

Alloys: The conductance of alloys, such as brass (copper and zinc) or bronze (copper and tin), can differ significantly from that of the pure metals they are made from. The specific combination and concentration of alloying elements will affect the overall conductance.

C. The Number of Valence Electrons per Atom

Free Electron Density: The number of valence electrons per atom determines how many electrons are available to move freely through the metal. More valence electrons generally mean a higher density of free electrons, which enhances conductivity. For example:

Copper has one valence electron per atom, which contributes to its high conductivity.

Gold also has a high number of free electrons, contributing to its excellent conductive properties.

D. Temperature

Effect on Conductance: For most metals, conductivity decreases with increasing temperature. This happens because:

Increased Lattice Vibrations: As temperature rises, the metal's lattice vibrates more intensely, causing more collisions between electrons and atoms.

Electron Scattering: More scattering reduces the mobility of free electrons, leading to decreased conductance.

However, for some materials, such as superconductors, temperature can affect conductance differently (e.g., conductivity increases when cooled below a certain critical temperature).

E. Number of Ions

Relevance to Ionic Conductors: The number of ions affects conductance primarily in ionic solutions and electrolytes. In these cases:

Ionic Conductors: Conductance depends on the concentration of ions in the solution, as more ions lead to higher conductance.

Metallic Conductors: For metals, the number of ions is less relevant since the conduction is primarily due to the flow of free electrons rather than ions.

Summary

The factors affecting electronic conductance in metallic conductors are:

A. The Nature and Structure of the Metal: Influences the density of free electrons and the ease of electron movement.

B. The Composition of Metallic Conductor: Impurities and alloying elements can disrupt electron flow and affect conductance.

C. The Number of Valence Electrons per Atom: More valence electrons usually enhance conductivity.

D. Temperature: Increasing temperature typically decreases metallic conductance due to increased electron scattering.

E. Number of Ion is not directly relevant to metallic conductors but is crucial in ionic conductors.

Therefore, for metallic conductors, the relevant factors are A, B, C, and D, making option 2 the correct answer.