# Energy levels help needed!! A-Level Physics.

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#1
In gases, the line spectra are fairly simple and atoms consist of just a few and fairly separated energy levels, I get thats because atoms are isolated in a gas and far away.

What causes the energy levels to be complicated for solids? I understand that there are a lot of atoms together which interact, but unsure about how that really gives rise to an energy band.

Also, are the energy levels in a particular solid the same for every atom in the solid (same question for the atoms in even gases)? Or each atom in a gas/solid has different energy levels/energy band compared to another atom?
Last edited by username5055262; 1 year ago
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1 year ago
#2
(Original post by CruduxCruo)
In gases, the line spectra are fairly simple and atoms consist of just a few and fairly separated energy levels, I get thats because atoms are isolated in a gas and far away.
(Original post by CruduxCruo)
…What causes the energy levels to be complicated for solids? I understand that there are a lot of atoms together which interact, but unsure about how that really gives rise to an energy band.
It is the enormous number of electrons and the number of interactions that make the “physics” complicated. In the “simplified” version, it is still “pretty ugly” in my opinions.

An isolated hydrogen atom has discrete energy levels. When 2 hydrogen atoms are brought close together, they can form a molecule. As they are separated by a distance of say r0, the energy levels are still pretty separated: there are 2 isolated atoms “1s” energy level, 2 “2s” energy level, etc…
When 4 atoms are brought closer together, there are 4 isolated atom “1s” energy level, 4 the “2s” energy level, etc…
When N atoms are brought closer together, note that this N is very large, which is in the order of 1023, this means that at the 1s energy level, there are 1023 “lines”, these 1023 “lines” form what is known as band.

(Original post by CruduxCruo)
Also, are the energy levels in a particular solid the same for every atom in the solid (same question for the atoms in even gases)? Or each atom in a gas/solid has different energy levels/energy band compared to another atom?
Not really sure what are you asking here.

The energy level in a solid (usually known as bandstructure) depends on a few factors: how atoms are arranged, number of valence electrons, is the solid-insulator, semiconductor or metal, etc.
In a solid, we don’t really talk about the energy level of an atom because it does not make sense.
In gas of hydrogen atoms, the energy levels of a hydrogen atom are “usual” energy levels of an isolated hydrogen atom.
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