Question

What is a valence band?
A. The energy band formed from those energy levels of the atoms which contain the valence electrons is called the valence band.
B. The lowest unfilled energy band formed just above the conduction band.
C. The lowest unfilled energy band formed just beside the conduction band.
D. partially- filled band above the completely- filled lower bands.

Answer 1

Hint :In order to answer this question, to know the correct definition in the given options, we should have gone through the whole concept of the valence band. We will also discuss some other important properties or applications of valence band.

Complete Step By Step Answer:
Energy band is the range of energies of a group of electrons in an atom. The lowest value of that range is the energy of the lowest energy electron and highest value is that of the highest energy electron. Valence band is an energy band of the electrons in the outermost orbit of an atom. Such electrons are called Valence Electrons.
The valence band is basically the outermost electron orbital of an atom of a particular material that electrons really possess. This is firmly identified with the possibility of the valence electron. The energy distinction between the most noteworthy involved energy condition of the valence band and the least abandoned condition of the conduction band is known as the band hole and is demonstrative of the electrical conductivity of a material. And, the degree to which it is filled largely determines the material’s electrical conductivity. In a typical conductor (metal), the valence band is about half filled with electrons, which readily move from atom to atom, carrying a current.
Hence, the correct option is (A.) The energy band formed from those energy levels of the atoms which contain the valence electrons is called the valence band.

Note :
It is made up of those valence shell orbitals which have electrons in them. For example, a sodium valence band is made up of $ 3{s^1} $ orbital. The electronic configuration of sodium is $ 1{s^2},2{s^2}2{p^6},3{s^1} $ .