Prologue/Rant about online classes
We have been taught the electron sea model to explain metallic bonding and conduction of electricity by metals. Then out of the blue, the band theory was introduced, without even giving the definition of what a band is. So I was lost in the recorded online class with no method of asking a doubt. So in an attempt to not wait a day for asking the doubts, I took it on myself to clear my doubts. So I surfed through the web and almost reached a conclusion.. before referring to a textbook.
The actual doubt
So as far as I know, the MOs (on a large scale, like 10 raise to 23 atoms scale) having similar energies appear as bands. The outermost band of occupied MOs is called the valence band. But what I am confused about is what makes up the conduction bands. I reached a conclusion from the chemistry libre texts that conduction bands are made from the combination of the unoccupied atomic orbitals. But when I referred to my reference book, it stated that they are the anti bonding MOs of the valence band.
So what actually makes up the conduction band? Is it one of the two I mentioned above? Or is it a theoretical set of energy levels where an electron can move freely to conduct electricity?