Author Question: When examining the electrical and thermal conductivity of a metal, you find that only the conduction ... (Read 76 times)

Medesa · **on:** Jul 28, 2018

When examining the electrical and thermal conductivity of a metal, you find that only the conduction electrons truly contribute to these conductivities. Choose the statement below that most specifically details the property of atomic electrons that allows them to become conduction electrons and to contribute to these conductivities.
a. They are close in energy to the Fermi energy.
b. They are closely (or strongly) bound to the atomic nuclei and therefore lie lower in energy.
c. Their spin magnetic moments are aligned.
d. The attraction to positively charged ions and repulsion from negatively charged ions accelerates them through the metal carrying energy.
e .As the ions separate due to thermal expansion, all electrons become conduction electrons as they move further from nuclei.

Question 2

Which of the following is NOT a true statement about the relationship between the thermal expansion of a solid and the potential energy of an ion in a solid?

ebonylittles · **Reply #1 on:** Jul 28, 2018

Answer to Question 1

a.
Only those electrons close in energy to the Fermi energy will be able to be excited enough to contribute to the thermal and electrical conductivity. All other electrons are too strongly bound to have a significant probability of becoming excited enough to carry energy within the atom.

Answer to Question 2

c.
This statement is not true. Ions oscillate from the minimum separation as the temperature increases, but their energy is not exactly that of a simple harmonic oscillator. The potential energy curve for an ion in a solid is not symmetrical about the minimum separation. In a simple harmonic oscillator, the potential curve is completely symmetrical. The asymmetry of the ion's curve leads to thermal expansion.