What is the difference between valence and conduction bands in metallic bonding?

In summary, metallic bonding involves the formation of bands of orbitals, with the valence band being the highest filled level and the conduction band being the first unfilled level. For a transition metal like Cr, the valence band can vary and is not necessarily full. The position of the Fermi energy also plays a role in determining the distribution of electrons in the valence and conduction bands. In metals, the Fermi energy often causes the conduction and valence bands to overlap, allowing for easy movement of electrons.
  • #1
Chemist20
86
0
hello,
i have a question related to metallic bonding.

As far as i know, valence band is defined as the highest filled level in the band and conductionband as the 1st unfilled level. So, if I have 100 Li, we will have 100 orbitals which form a band. Since we have 100electrones, 50 pairs, so we occupy half of the band right? then... valence band would be level 50 and conduction band 51? or is it more like: the all the filled leves form de valence band and all the empty ones the conduction band?Also, for a transition metal for example, what would the valence bond be for eg Cr? i mean, how do you define valence band? does it always have to be full?
 
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  • #2
You have to look not only at the available states as bands but also at the distribution probability (Fermi-Dirac for electrons)

The position of Fermi energy determines to which level electrons are filled at 0 K. The Fermi energy can be in the valence band/conduction band and the states till that level is filled.

It so happens that for metals, at the Fermi energy, both the conduction and valence bands overlap. Basically there is no energy higher than the thermal energy required for electrons to move in the conduction band.

You might check this page
http://hyperphysics.phy-astr.gsu.edu/hbase/solids/band.html
 

1. What is the difference between valence and conduction band?

The valence band is the highest energy level occupied by electrons in a material, while the conduction band is the lowest energy level that is not occupied by electrons. Electrons in the valence band are bound to the atoms in a material, while electrons in the conduction band are free to move and conduct electricity.

2. How do valence and conduction bands affect the properties of a material?

The position and width of the valence and conduction bands determine the electrical and optical properties of a material. Materials with a larger band gap between the two bands are insulators, while materials with a smaller band gap or overlapping bands are conductors or semiconductors.

3. What is the significance of the band gap in electronic devices?

In electronic devices, the band gap plays a crucial role in determining the conductivity and switching behavior of the material. Materials with a small band gap, such as semiconductors, are commonly used in electronic devices to control the flow of electricity.

4. How does temperature affect the valence and conduction bands?

Increasing the temperature can cause the valence and conduction bands to overlap, allowing more electrons to move and increasing the conductivity of the material. This is known as thermal excitation and is the basis for the operation of thermoelectric devices.

5. Can the position of the valence and conduction bands be altered?

Yes, the position of the valence and conduction bands can be modified by doping the material with impurities or by applying an external electric field. This can change the band gap and alter the electrical properties of the material, making it useful for different applications.

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