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), (C) and (D) only
Understanding Electronic Conductance in Metals
Electronic conductance refers to the ability of a material to conduct electric current through the movement of electrons. In metals, free electrons act as the charge carriers. Several factors influence how easily these electrons can move through the metallic structure.
Analyzing Factors Affecting Electronic Conductance
Let's examine each factor listed in the options to determine its impact on electronic conductance:
- (A) The nature and structure of the metal: Different metals have different atomic structures and electron configurations. The arrangement of atoms in the crystal lattice and the binding energy of electrons vary from metal to metal. This inherent nature and structure directly affect the availability and mobility of free electrons, thereby influencing the electronic conductance. For example, copper and silver are good conductors because of their structure and electron arrangement, while iron is less so. This statement is a valid factor.
- (B) Composition of metallic conductor: While related to the "nature" of the metal, composition specifically refers to the elements present, especially relevant in alloys (mixtures of metals). Different compositions lead to different structures and electron arrangements, which in turn affect conductivity. However, compared to the fundamental nature/structure, the number of valence electrons, and temperature, composition is often considered part of the material's inherent nature. In the context of the given options and the provided correct answer, this factor is not listed as a primary, distinct factor among the correct choices.
- (C) The number of valence electrons per atom: Valence electrons are the electrons in the outermost shell of an atom and are often the ones that become 'free' and contribute to electrical conductivity in metals. A higher number of readily available valence electrons per atom often leads to better electronic conductance, provided they are mobile within the lattice. This statement is a crucial factor.
- (D) Temperature: Temperature significantly affects electronic conductance. As temperature increases, the atoms within the metal lattice vibrate more vigorously. These vibrations, known as phonons, scatter the moving electrons, impeding their flow. This increased scattering reduces the mobility of electrons, thus decreasing the electronic conductance. This statement is a valid factor.
- (E) Number of ions: Electronic conductance in metals is due to the movement of negatively charged electrons, not positively charged ions. Movement of ions is responsible for ionic conductance, which occurs in electrolytes or molten salts. Metals conduct electricity electronically. Therefore, the number of ions is not a factor affecting electronic conductance in metals. This statement is not a valid factor.
Summary of Factors for Electronic Conductance
Based on the analysis, the factors that directly influence the electronic conductance in metals from the given options are:
- (A) The nature and structure of the metal
- (C) The number of valence electrons per atom
- (D) Temperature
The provided correct answer aligns with this analysis, identifying (A), (C), and (D) as the correct factors.
| Factor | Effect on Electronic Conductance | Relevance |
|---|---|---|
| (A) Nature and Structure of Metal | Determines electron availability and lattice scattering | Relevant |
| (B) Composition of Metallic Conductor | Related to nature (especially in alloys), influences structure | Less primary as a distinct factor in this list |
| (C) Number of Valence Electrons | Provides the charge carriers (electrons) | Relevant |
| (D) Temperature | Increases lattice vibrations, scattering electrons | Relevant (Conductance usually decreases with temp.) |
| (E) Number of Ions | Ions are involved in ionic conductance, not electronic | Not Relevant (for electronic conductance) |
Revision Table: Key Concepts in Electronic Conductance
| Factor | Why it matters for Electronic Conductance |
|---|---|
| Metal's Nature/Structure | Impacts how electrons move through the atomic lattice. Different structures offer different resistances. |
| Valence Electrons | These are the 'free' electrons that carry the current. More free electrons generally mean better conductivity. |
| Temperature | Higher temperature causes atoms to vibrate more, scattering electrons and reducing flow. |
Additional Information: Types of Electrical Conductance
It's important to distinguish between electronic conductance and ionic conductance.
- Electronic Conductance: This is the flow of electric current through the movement of electrons. It is typical in metals and semiconductors. Factors include the material's nature (structure, composition), presence of free charge carriers (electrons), and temperature.
- Ionic Conductance: This is the flow of electric current through the movement of ions (charged atoms or molecules). It occurs in electrolytes (like salt solutions) and molten ionic compounds. Factors include the concentration of ions, mobility of ions, and temperature (higher temperature usually increases ion mobility and thus ionic conductance).
The question specifically asks about electronic conductance, making the number of ions irrelevant.
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